Sometimes called blue-tailed skink, but don’t confuse it with the one native to Australia. This is Plestiodon fasciatus, better known as the common 5-lined skink.  It’s one of the most common lizards in the eastern part of the US.  Only the juveniles have this characteristic blue tail.

I could write more, but I’ve no pretensions of being an herpetologist and would just be parroting information read elsewhere.  Here’s a nice little writeup about this reptile.  Here’s another.