Not all people across the world shake hands. This is a tradition that is slightly more common in the West. However, it has spread to many different regions of the world.
Handshaking is particularly common in business settings, although in some countries, handshaking is common even in casual situations. It is not clear which region first introduced the handshake, but this has been common since Antiquity, and there is evidence of Greek people shaking hands as far back as the 5th century BC. It is believed that handshakes originated as a way to show that the person had no weapons or that he was not planning to attack.