A robber is a person who steals or takes something belonging to someone else. Robbers use force or threats to take what they want. A bank robber is someone who steals money from a bank. When the robber takes something, this is called a robbery. One famous robbery was the Great Train Robbery in England. Armed robbery means that the robber used a weapon such as a gun in the robbery. Many robbers have become infamous, such as Jesse James in America and Ben Hall in Australia. Australian robbers used to be called bushrangers.
The word "rob" comes from a Latin word, deraubare. This word came from a German word raub which means clothes. Before clothes were made in factories and became cheap, robbers often took a person's clothes.