Angle shooting is a move at the poker table used to gain an unfair advantage over your opponent.
Even though angle shooting is not against the official poker rules, it is considered unethical and is looked down upon in the poker world.
String betting, hiding high denomination chips, or glancing to see your opponent's cards is just a few examples of poker angle shoot and something you should avoid doing and protect yourself from other players trying to use any of these tricks against you.
You will mostly face angle shooting in live games, so always be on the lookout and protect your cards and chips as much as possible. It is worth mentioning that some poker room managers can even ban players who try to angle shoot, while others can ignore this whatsoever. At the end of the day, you are responsible for yourself.