Why do we shake hands as a form of social greeting? How this practice started is not really known, but many historians believe that shaking another person’s hand arose out of the tradition of displaying an open palm to a stranger to signify it held no weapon. Eventually the gesture became symbolic rather than practical.
Nowadays, shaking hands does not mean because you met someone new. You shake hands with an old friend whom you haven’t seen for a long time. You shake hands with a business partner when a deal has been completed.
The nuances of the handshake are actually different in cultures worldwide. The French generally kiss both cheeks as a greeting, reserving the handshake for business deals. Russians shake hands, but never when wearing gloves. The Japanese shake hands often, but sometimes substitute bowing instead; and lingering, limp handshakes are the norm in Arab cultures.