What is the meaning of the integral notation with a circle in the middle?

[DeepSeeded]

I can't find a description for the Integral notation with a circle in the middle and sometimes a letter in it I think. I do not see any mention of it on wikipedia or in my calc classes. There it is ----> \oint

 

[Crosson]

http://en.wikipedia.org/wiki/Line_integral

 

[DeepSeeded]

http://en.wikipedia.org/wiki/Line_integral

Oh, a closed line interval. Got it thanks!