An ally is a person is who works towards understanding and supporting the LGBTQIA+ community, and believe that everyone has the right to choose who they are in terms of gender identity, gender expression and sexual orientation. Someone who makes an effort and provides a non judgmental space for people to express themselves. Being an ally is a continuous process as understanding sexuality is a continuous process. One can be a part of the LGBTQIA+ community and be an ally.
Sources:
https://au.reachout.com/articles/what-is-an-lgbtqia-ally-and-how-can-i-be-a-good-one