Non-binary people have a gender identity that sits outside of the (socially constructed) binary where male and female are the only options.
A non-binary person might use gender neutral pronouns they/them, or they might use he or she. They have no legal recognition in the UK.
Non-binary people may or may not also identify as trans people. You cannot say you support trans rights and trans people if you don’t support non-binary people as part of that.
I’m also thinking today of my non-binary colleagues and friends. As a friend commented on my piece about trans role models, all trans (including non-binary) people are role models for being themselves when the world constantly tells them not to be.