What is Agender?
Agender is a gender identity. It falls under the "non binary" umbrella, referring to genders other than male or female. Other gender identities commonly falling under the umbrella term non binary include genderqueer, genderfluid, neutrosis, and more.
How can someone not identify as male or female? It comes down to self determination. Some people do not feel that they relate to these rigidly defined binary identities. Some people feel like they relate to both. Agender people, and other non binary people, identify as such for a diverse set of reasons. Agender people may or may not identify as transgender.
As an agender person, I do not feel a strong pull to either gender. I embody a neutral gender. I prefer they/them or he/him pronouns.