This is a Green Anole, one of my favorite lizards. As a child, I looked forward to the county fair every year, where you could buy anoles as pets. My terrarium always had several.

The red throat flap is called a dewlap, and it is used to attract a mate, and as a challenge to other males. When two males meet, they flash their dewlaps and start doing pushups, raising and lowering their bodies. This continues until one of them decides he has lost and runs away.