A cricket match will almost always have two umpires who control the game on field. It may have additional umpires who control television reviews and act as substitutes if needed, plus a referee who reports on disciplinary issues.
Almost every match will have two on-field umpires, who have equal status (meaning there is no “first umpire” and “second umpire”). They will each stand at the same end of the pitch during the game. During an over, the umpire standing at the bowler’s end (usually just behind the stumps) is in charge of deciding whether a player is out, keeping track of the six legal balls in an over, signals scoring and any other key decisions. The umpire at the other end, who usually stands in or near the square leg fielding position does not make decisions but supports the other umpire with information where needed. Because the umpires don’t change ends, they will naturally alternate who is the bowler’s end umpire in each over.
Normally the bowler’s end umpire will concentrate on whether the delivery is lawful (for example if it’s a no ball or wide), LBW, and run-outs at the bowler’s end. The other umpire will concentrate on stumpings and run-outs at the strikers’ end (the end where the batter receives the delivery), though they can call a no ball for arriving too high.
Some games, most usually internationals will have a third and often a fourth umpire. The third umpire is in charge of television reviews such as the Decision Review System (DRS). They will also act as a substitute if one of the two on-field umpires is injured or ill.
The fourth umpire is in charge of managing the balls (including bringing on a new one when necessary), taking drinks to the on-field umpires during a drink break, plus technical tasks such as checking the batteries in a light meter. The fourth umpire will take over the television review role if the third umpire has to substitute for an on-field umpire.
Some games, most usually internationals, also have a referee. They play no role in the management of the game itself and are not classed as one on the umpires. Instead they track whether players have followed the ICC Code of Conduct and report any disciplinary breaches. They often also write a report on the condition of the pitch.