That brings up a couple more questions. Where are the umpires positioned and is there replay for questionable calls?
One umpire stands at the bowlers end and faces the batter. That umpire adjudicates on 'wide' deliveries and 'no ball's deliveries, especially if the bowler puts their front foot over the line.
When the ball had been bowled, that umpire moves off to the side and stands at right angles to the pitch, in line with the batting line (crease).
The second umpire stands at right angles to the pitch and is in line with the side of the batter.
There is also a 'third umpire' who is off field and does video adjudication for the tricky calls.