Aiding and abetting generally means to somehow assist in the commission of a crime, or to be an accomplice. It involves a plan to commit a crime or to commit acts, the probable consequences of which are criminal.
An accomplice may assist or encourage the main offender with the same intent to have the crime committed, but does not necessarily have to be present when the crime is actually committed. However, without sharing the criminal intent, one who is merely present when a crime occurs and stands by silently is not an accomplice, regardless of the harm that could've been prevented if he/she had acted.
