This is a squirrel on my patio as he's about to take a banana chip I'm holding.

I was bit by a squirrel when I was a child, when I held out a cupped hand of acorns. Since their eyes are on the sides of their head, they can't see in front of them at close range. They bite in the general direction of the food. I only offer food to those squirrels that use care when taking it, and I keep my fingers out of the way (e.g. I use large pieces of food like this banana chip).