How can i understand if the other player is cheating?

i joined today so i dont know much

Just presume they aren't if their rating isn't 2000+.

also what is meant by cheating? like using what?

Also presume they are not cheating if their rating is above 2000.

All such discussion goes here:

http://www.chess.com/groups/forum/cheating-forum

Using chess programs to play their moves. They will input your moves against a strong program and play against you whatever move the computer plays.

But if they are doing this, their rating will likely be high. I don't believe I've ever played someone who is cheating here.