The following is a list of geometric symbols commonly used in geometric proofs similar to those on this site and what they mean.  Normally, I would have written them in the proofs and explained them to you, but the text in Microsoft Paint does not allow for such luxuries!  (That's Microsoft for you!!)  Anyway, here they are (and of course this is not necessarily a full list). 
              Proof Symbols
Proof Examples
Fillin (Practice) Proofs