A sign language (also signed language) is a language which chiefly uses manual communication to convey meaning, as opposed to spoken language. This can involve simultaneously combining hand shapes, orientation and movement of the hands, arms or body, and facial expressions to express a speaker's thoughts.
Wherever communities of deaf people exist, sign languages have developed, and are at the cores of local deaf cultures. Although signing is used primarily by the deaf, it is also used by others, such as people who can hear but cannot physically speak, or have trouble with spoken language due to some other disability.
It is not clear how many sign languages there are. A common misconception is that all sign languages are the same worldwide or that sign language is international.
Learning sign language isn't an easy thing, and couldn't be learned in only one day. But learning it will be very useful, in case one day you end up meeting a deaf/mute person in am emergency situation.
So guys, to be able to live and learn something for the sake of helping and supporting someone is something that everyone should do! It's being human, it's saving a life!