All About Umpires and Signals

Umpires-
           There are 3 umpires in cricket. Two on ground and one is out of the ground who helps onfield umpires to give decisions on crucial times. In cricket, an umpire is a person who has the authority to make decisions about events on the cricket field, according to the Laws of Cricket. Besides making decisions about legality of delivery, appeals for wickets and general conduct of the game in a legal manner, the umpire also keeps a record of the deliveries and announces the completion of an over.
A cricket umpire is not to be confused with the referee who usually presides only over international matches and makes no decisions affecting the outcome of the game.

Umpire Signals-

1)Out-

An umpire will not give a batsman out unless an appeal is made by the fielding side, though a batsman may walk if he knows himself to be out. The umpire's response is either to raise his index finger above his head to indicate that the batsman is out, or to clearly say "not out"

2)No ball-

Either umpire may call, and signal, no-ball, for a ball that is illegally delivered bowled. 
Causes for no-balls are foot faults or a ball passing above a batsman's waist without bouncing. The 
 signal is to hold one arm out horizontally and shout "no-ball"

3) Free hit-

In certain forms of limited-overs cricket, such as T20s and ODIs, a no-ball that is the result of the bowler overstepping the crease or bowling above a batsman's waist will be penalised by the next delivery being subject to limited methods of dismissal. The umpire will signal this by circling a finger horizontally over his head

4)Wide-

A Wide Ball is an illegal delivery in cricket, due to it being "wide of the striker where he is standing and would also have passed wide of him standing in a normal guard position" . A wide  signalled by extending both arms out horizontally and is accompanied by a call of Wide Ball. 

5)Dead ball-

If the ball is no longer considered in play it is a dead ball. An umpire will signal this by crossing and uncrossing his wrists below his waist with the call Dead Ball 

6)Four-

If a batsman scores four when he hits the ball across the boundary (not by actually running them), the umpire signals this by waving his arm back and forth in front of the chest. 

7)Six- 

A six scored by hitting the ball over the boundary is signalled by the umpire raising both hands above his head, often in a celebratory manner. For a six to be scored, the ball must come off the bat, so it is impossible to have six byes for a ball crossing the boundary (without there being overthrows).

8)Bye-

If runs are to be scored as byes, the umpire will hold up one open palm above the head.

9)Leg bye-

Leg byes are signalled by the umpire touching a raised knee.

10)Short run-

If one of the batsmen turns to complete runs after the first without grounding his person or equipment behind the popping crease, then a short run is signalled by the umpire tapping his near shoulder with his fingers and the short runs are not scored. If more than one run is short, the umpire will inform the scorers as to the number of runs scored. There is also a case of deliberate short running, where the umpire will disallow all runs, although this is a rather rare occurrence.