Stealing, in Hebrew geneba is when I take something that doesn't belong me without the owner of that object knowing. While robbing, gezela, is to take something from a person by force. Someone can steal your belongings when you're not home. However, if a person approaches you on the street and forces you to give them your watch, you have been robbed.
In both cases, the perpetrators must restitute the object they took or its monetary value to its owner. But in ancient Jewish Law, the one that stole (sic) had to pay twice the value, while the one that rob had to restitute just whatever he took by force (this point will be explained later on).
Stealing is forbidden regardless of the value of the object I take. Even if I steal something of an insignificant monetary value (pachot mishave peruta) I have perpetrated and act of stealing. Moreover, even if I take something temporarily from somebody else, i.e., I said to myself that I’m borrowing an object to use it for a while without the owner's knowledge and with the intention to bring it back to him, it is still considered stealing.
It is forbidden to steal from a fellow Jew or from a gentile. If the gentile made a mistake and, for example, gave me extra change, although it is technically his mistake and legally I could hold the extra money, it might be an opportunity to fulfill one of the most important Mitzvot of the Tora: Kiddush haShem, sanctifying God’s name. Which will happen when a non Jew would see an exemplary moral behavior of a Jew and would be inspired to praise God for having given the Jewish people a Law of fairness and wisdom (=The Tora). Furthermore, according to Sefer haChasidim those who made money out of a mistake of a gentile did not see any blessing from it.
“Fortunately they were able to painstakingly put the pieces of their lives back together.
by Toby Klein Greenwald