What means centipawn Loss?

I'm sure someone else already ask the same question on this forum, but I could not find it.

My question is simple:
What means the Centipawn Loss? How to improve it?

http://en.lichess.org/qa/103/what-is-average-centipawn-loss
Thibault answered it.

Thank you so much, exactly what I was looking for.

Ah yes, sure, as it was one thing of Game Analysis I thought it was here. Sorry.