If you are unfamiliar with the term "borb," then here's a quick primer of how this particular bit of internet slang came to be.
First, there were birds. Birds are cute, and as is the way of all cute things on the internet, they were awarded the moniker of "birb." Later, someone noticed how round birbs looked rather like orbs.
And thus, the "borb" was born. All borbs are birbs, but not all birbs are borbs. All are also, technically, birds, but where's the fun in that?