Trans* is an umbrella term that refers to all of the identities within the gender identity spectrum. There’s a ton of diversity there, but we often group them all together (e.g., when we say “trans* issues). Trans (without the asterisk) is best applied to trans men and trans women, while the asterisk makes special note in an effort to include all non-cisgender gender identities, including transgender, transsexual, transvestite, genderqueer, genderfluid, non-binary, genderfuck, genderless, agender, non-gendered, third gender, two-spirit, bigender, and trans man and trans woman.
The origin behind the asterisk, as I understand it, is a bit computer geeky. When you add an asterisk to the end of a search term, you’re telling your computer to search for whatever you typed, plus any characters after (e.g., [search term*][extra letters], or trans*[-gender, -queer, -sexual, etc.]). The idea was to include trans and other identities related to trans, in the most technically awesome way. I <3 Geekdom.
I created the graphic below to help raise awareness of this so folks can be more inclusive in their writing when referring to trans* people. Share the original post on Facebook if you pledge to write “trans*” from now on.