Extras

Additional runs can be gained by the batting team as extras (called "sundries" in Australia) due to errors made by the fielding side. This is achieved in four ways:
No ball – a penalty of one extra that is conceded by the bowler if he breaks the rules of bowling either by (a) using an inappropriate arm action; (b) overstepping the popping crease; (c) having a foot outside the return crease. In addition, the bowler has to re-bowl the ball.
Wide – a penalty of one extra that is conceded by the bowler if he bowls so that the ball is out of the batsman's reach; as with a no ball, a wide must be re-bowled
Bye – extra(s) awarded if the batsman misses the ball and it goes past the wicketkeeper to give the batsmen time to run in the conventional way (note that the mark of a good wicketkeeper is one who restricts the tally of byes to a minimum)
Leg bye – extra(s) awarded if the ball hits the batsman's body, but not his bat, and it goes away from the fielders to give the batsmen time to run in the conventional way.
When the bowler has bowled a no ball or a wide, his team incurs an additional penalty because that ball (i.e., delivery) has to be bowled again and hence the batting side has the opportunity to score more runs from this extra ball. The batsmen have to run (i.e., unless the ball goes to the boundary for four) to claim byes and leg byes but these only count towards the team total, not to the striker's individual total for which runs must be scored off the bat.