These are some nouns which are similar to one another, we may learn about them, in order to distinguish.

burglar robber shoplifter pickpocket mugger thief

A burglar is someone who breaks in and steals from a private home.

A robber is someone who breaks in and steals from, e.g., a bank or business.

A shoplifter is someone who steals something when he/she is in a store.

A pickpocket is someone who steals from you on the street, often without you noticing.

A mugger is someone who uses violence to steal from you on the street.

A thief is the general word for some who steals.

All of them are related to steal, though the ways they work are different.

from American English File - MultiPack 4A
No, a burglar needn't steal anything (commit robbery). The act of breaking in is 'burglary'.

A robber needn't break in (commit burglary). The act of stealing is 'robbery'.

If you break in but steal nothing, you are guilty of burglary.

If you break in and steal something, you are guilty of burglary and robbery.

If the door is open, and you walk in and steal something, you are guilty of robbery.

If the door is open and you walk in, but you steal nothing, you are guilty of neither crime (though you may be guilty of trespassing.)
Thank you for the opinion.
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Hi,

A robber is someone who steals, usually with violence or the threat of violence. The type of place does not matter.

A pickpocket is someone who steals from your pocket, stealthily. It doesn't have to be on the street.

For more precise details, you'd have to look at the criminal laws of a particular country.

Clive