What kind of turtle is this?

[UpInTheClouds]

http://tinypic.com/r/2ewmj6a/8

[Oregon_Gal]

That is a Red Eared Slider Turtle. It is a semi aquatic and has very specific needs. The specific turtle in your picture is a female probably about two years old.
If it is a pet, you need to do a LOT of research before keeping it.
Because it's a female this turtle will mature to over a foot in shell length.

http://redearslider.com
https://www.facebook.com/groups/550812271651212/
https://www.facebook.com/RedEarSlider

These are a few links to forums and groups specifically to this type of turtle.

I strongly recommend that if you caught her out of the wild, that you return her where you found her and enjoy her in her natural habitat.
In many places in the USA she is not legal to buy, sell or release.