Theft, robbery and dacoity are three types of crimes under the law on crimes known as the Indian Penal Code, 1860.
Theft is when someone steals a movable property out of your possession with the intention of stealing it from you. For example, if Shikar steals five hundred rupees from your wallet when you were not in the room, then it is an act of theft.
Robbery is an aggravated form of theft, so if someone attempts or causes any hurt, wrongful restraint or death in order to commit an act of theft, it is known as robbery. For example, if Shikar comes to your house, beats you up and then steals five hundred rupees from your wallet, it is an act of robbery.
Dacoity is a crime when 5 or more people commit or attempt to or aid someone to commit an act of robbery together. For example, if Shikhar and his 4 friends come to your house and beat you up to steal your money and jewellery, then it is an act of dacoity.
The punishment for these crimes are also different. If you commit theft you may be punished with jail time up to 3 years or a fine or both. If you commit robbery you may be punished with jail time up to 10 years or a fine or both. If the robbery is committed on the highway between sunrise and sunset then the jail time may be up to 14 years. If you commit dacoity then you may be punished with jail time which may be for life and a fine.