A little question

[Moontribe]

Hello,

i'm playing the piano for about a month now and i have a problem. This is maybe a "newbie" question, but i have no teacher, so maybe you guys can help me out. I've downloaded a sheet tab and i don't know what those "C" mean (look at the pic):



Can somebody tell me what it is? And what i have to do?

Btw: i'm now at my fathers home, and here i got no Piano but a Keyboard (... it's better then nothing).

Tnx!!

[donjuan]

Common time - Same as 4/4
4 quarterbeats per measure.

[Moontribe]

I see, tnx for your reply!