LGBTTQQIAA2P+ -- the longest version of the acronym that I could currently remember. From left to right, the letters denote: lesbian, gay, bisexual/biromantic, transgender, transsexual, queer, questioning, intersex, asexual, aromantic, two-spirit, pansexual/panromantic, etc. Will most likely be subject to updates. More common versions include "LGBT", "GLBT", "LGBTQ", "LGBTQIA+" etc. The word "queer" is commonly used as a condensed umbrella term, and is usually favored as it does not leave any identities unaccounted for (also recognize that some individuals still view the word "queer" as a derogatory slur. It is wise to check with the individuals around you to make sure that no one is triggered or made upset by the use of the word.) There are some debates about what the "A" stands for in many of the acronyms, in terms of whether it means "asexual" or "ally". While straight and cisgender allyship is imperative to the safety and success of the LGBTQIA+ community, it is recognized by many queer individuals that allies are not queer themselves, and therefore are not represented in the acronym.

• Ace Spectrum -- a continuum that contains all ace identities, including asexual, greysexual, demisexual, aromantic, greyromantic and demiromantic.
  • Aromantic -- an individual that does not experience romantic attraction.
  • Asexual -- an individual that does not experience sexual attraction.
  • Demiromantic -- an individual that only experiences romantic attraction to a person after forming an emotional bond with said person.
  • Demisexual -- an individual that only experiences sexual attraction to a person after forming an emotional bond with said person.
  • Greyromantic -- an individual who experiences romantic attraction very rarely or under very specific circumstances.
  • Greysexual -- an individual who experiences sexual attraction very rarely or under very specific circumstances.
• AFAB -- "Assumed Female At Birth", meaning an individual that was pronounced a girl at birth, regardless of current gender identity.
• Agender -- the state of not having a gender identity. This identity is under the genderqueer umbrella.
• Ally -- a heterosexual cisgender person that supports the queer community (in practice -- not just in words).
• AMAB -- "Assumed Male At Birth", meaning an individual that was pronounced a boy at birth, regardless of current gender identity.
• Androgyny/ous -- being neither masculine or feminine. Some genderqueer/non-binary people will use this as an identity term, but it is also an adjective.
• Androsexual -- the state of being attracted to men or masculinity.
• Binary genders -- a binary gender is a gender that is "boy" or "girl".
  • Cisgender -- an adjective used to describe individuals that currently identify with the gender they were assigned at birth. Can be separated into two smaller categories, "cisgender boy" and "cisgender girl". Sadly, most human beings do not anticipate that their infants will be born non-binary or genderqueer, so at this point, cisgender identities are limited to the binary genders.
• Bisexual -- the state of being attracted to individuals of your own gender and other genders.
• Faggot -- this word is a slur. This slur has been and continues to be used to demean gay and queer people. While the word holds other non-queer related meanings in other parts of the world, in western cultures it is widely seen as an insult to be used towards gay men. This word is also commonly used as a casual insult towards anyone who is AMAB and shows more feminine characteristics. While some queer people have reclaimed this word, it is widely still seen as a hurtful slur. A good ally would never say this word and would condemn its usage by non-queer people.
• Gay -- a word used to describe individuals who experience attraction specifically to individuals of their own gender. Usually denoting a self-identified man who is attracted to other self-identified men, "gay" can be used to describe homosexual women as well. Some individuals use this term as an umbrella word for their identity.
• Homosexual -- an adjective used to describe individuals that experience sexual attraction specifically to those of their own gender. This word, in the past, was used to describe the terrible "illness" that was being gay, and so some individuals prefer the word "gay" over this word.
• Intersex -- the "I" in LGBTQIA+ (etc.) A person who cannot be categorized as having strictly male or female genitalia, reproductive organs, sex hormones, etc. Many babies who are identified as intersex at birth have their genitals surgically altered to reflect one of the binary sexes; a process that 9 times out of 10 leads to crippling identity issues and a possibility for dysphoria going into the future.
• Lesbian -- a woman that is solely attracted to other women, be it sexually or romantically.
• Non-binary -- This adjective is used to describe individuals who do not subscribe to the traditional concept of binary genders, i.e. being a girl or a boy. Non-binary people can have a wide arrange of expressions; from feminine to masculine, both or neither. Despite this, these individuals still remain outside the "gender binary". Some non-binary identities include agender, androgynous, genderqueer, genderfluid, bigender, demiboy/girl, etc. Some individuals (like me) use the word "non-binary" as it's own identity term. Many people use the term "genderqueer" interchangeably with "non-binary" and this is perfectly fine.
• Pansexual -- the state of being attracted to individuals regardless of their gender. Can still denote preferences for certain physical traits, like masculinity, femininity, etc.
• Platonic attraction -- a non-sexual attraction that can be felt towards friends, family members, etc. A "friendship" attraction.
• Pronouns -- A pronoun is a word used to refer to a person without using their name. There are many different kinds of pronouns, for example: he/him/his, she/her/hers, they/them/theirs, etc. The "they/them/theirs" pronoun can be used singularly! It is commonly used by non-binary individuals who are not comfortable using a pronoun commonly associated with a binary gender. It is very nice and polite to ask a person what pronouns they use, regardless of whether they are trans and/or non-binary.
• Queer -- a partially-reclaimed word used as an ultra-inclusive umbrella term for the entire LGBTTQIA2+ community. While some individuals still react negatively to this word due to its history as a slur, it is a much more incusive word than any acronym out there.
• Questioning -- the 2nd "Q" in LGBTQQIA...+. A person who is questioning is someone who is considering their own possibility of being queer (regardless of which orientation or identity they're thinking about.) Questioning individuals could spend any amount of time in the deliberation period, whereas at the end of which they could decide whether they are queer or not.
• Romantic attraction -- a non-sexual attraction that can be felt towards love interests, partners, datemates, etc. An "in-love" attraction.
• Sexual attraction -- a non-platonic/romantic attraction that can be felt towards sexual partners, etc. A "Sim's "WooHoo™"" attraction.
• Tranny -- this word is a slur. This slur has been used historically and continues to be used towards openly trans individuals and perceivably gender-nonconforming individuals. While some queer people today have reclaimed this word and no longer see it as a slur, the large majority of queer people today are still made uncomfortable or triggered by the use of the word, whether it is used against them or not. A good ally would never say this word and would condemn its usage by non-queer people.
• Transfeminine -- A person who is transitioning to become more feminine, regardless of gender identity.
• Transgender -- this is a very broad term, albeit a simple one. A transgender person is any one person who's natal gender (birth gender) does not match or coincide with their identity gender (current gender). This encompasses FtM and MtF people, as well as some non-binary people who choose to refer to themselves as transgender. Some individuals who would otherwise fit in the transgender box choose not to adopt the label and this is perfectly fine. The choice to adopt the transgender identity label is completely up to the individual to decide, based on their own feelings and experiences. 
• Transmasculine -- A person who is transitioning to become more masculine, regardless of gender identity.
• Transsexual -- A transgender person who has undergone SRS (Sex Reassignment Surgery).
• Transvestite -- this word is a slur, but has not been used as a weapon to the extent that words like "tranny" and "faggot" have. This slur has been used historically to refer to sex workers who would cross-dress or transgender sex workers. This term is very old and has since been replaced by the much more sensitive and accurate terms "transgender" and "transsexual". I strongly urge allies to cut out the word "transvestite" from their vernacular, save for educational conversations.
• Two-Spirit -- the "2" in LGBTQQIA2...+. A translation of the Anishinaabeg (Ojibwa) term niizh manidoowag, referring to individuals who embody both a masculine and feminine spirit (via thecanadianencyclopedia.ca/en/article/two-spirit/).
  

As always, these definitions are perpetually under change and review and what might have been described as such 10+ years ago could be described in a very different way today. It is also important to recognize that identity is unique to every person, and every queer person has their own identity words that they're attached to. If you are an ally and want to accommodate your LGBTQ+ friend but are unsure how, it is always polite to ask!