What does it mean to be a brony?

There is a difference between being a অনুরাগী and being a brony(or pegasister). A অনুরাগী just watches the প্রদর্শনী and enjoys it, and that's fine. A brony is touched দ্বারা the প্রদর্শনী on another level, and therefore, joins the brony community. When you're a brony, friendship truly is magic. আপনি help your বন্ধু when they're in need, and stand up against those who try to put আপনি down. আপনি can have fun talking about MLP:FIM, লেখা fanfics, drawing pictures, RPing, and so much more.
That's what being a brony means to me. :)

Basically what DragonAura said.
Bronies/Pegasisters are really in touch with the show, as they know a ton about MLP and make a bunch of fanart of all sorts, like drawings, music, and fanfics. They talk about it on both internet and real life. Go to conventions like Bronycon and Everfree. Besides, it's not just those. It's believing the true meaning of friendship and happiness. Making বন্ধু near অথবা far.