A wide is another form of extra that accrues to the team's total apart from a no ball, bye and leg bye. A wide is declared when in the opinion of the umpire the delivery bowled is out of reach of the striker (so as to execute a legitimate stroke).
Although in Test cricket the umpires are lenient with the calling of a wide, they do a tight job when it comes to the One-day version, especially when the ball is drifting down the leg side.
The defaulting bowler is penalised with having to bowl an extra delivery apart from gifting away an extra run to the opposition. In the event of the wicket-keeper failing to gather the wide delivery, the batsmen are entitled to run additional runs.
In the event of the batsmen running a single, two wides shall be credited. One for the call and one for having run. So is the case when two/ three runs are run. In the event of the ball traveling all the way to the fence then four wides shall be declared.
The umpire shall signal a wide by spreading both his arms wide apart, holding it parallel to the ground.