Well as a Furry myself, i can explain the best i’d say.
Ya see there’s no simple definition aside from this.
Furry: a person/human who takes interest in anthropomorphic characters (animals that look like humans, Fox McCloud or Sonic the Hedgehog for example).
People usually mess up the definition of Furry and Anthro as they are similar. An antro is the character, the furry is the person who likes it.
Another misunderstood thing is that people think all Furries dress up as their very own character and want to get freaky with Anthropomorphic characters, this is not true.
Though about 30% of Furries wear fursuits, another 70% do not, i am one of these. The way i see it, there are about four stages to being a furry:

1) you find the Anthropomorphic design cool or attractive or whatever and take great interest in it, quite a few also get more intimate feelings about them too (I am at this stage)

2) you develop a ‘Fursona’ (1/10 worst word ever) in which is your Anthro alter ego.

3) you attempt Anthro based cosplay, wearing maybe only the mask or just some fake ears and a tail. At this point you’d be consumed by your fursona and would probably either bark, purr, hiss or something every now or then.

4) as if like the Flood infection, you are consumed by your uncontrollable desire to be a Fennec Fox and wear the full outfit, name yourself by the characters name and almost always act like the character. This is the critical stage most people judge furries by.

I recommend checking this one channel named ‘Kothtrix’ or sumthin’, i know i spelt it wrong but you’ll get there. He is a Furry much like me whose around stage 1 and a half, he can explain this sort of thing much better than me.