The bowler is next to the two batsmen the most important player. Without a bowler, no game can be played. The bowler delivers the ball to the striker. So the bowler is trying to throw/bowl the ball as fast as possible to make it difficult for the batsman to hit.
The bowler has two main objectives. His first and main objective is to get the batsman out; he should try everything, to get the batsman out.
The second objective the bowler has is to stop the batsman from scoring runs; because that is the only way the other team can win. A good bowler tries to meat these objectives during the time he is bowling.
Notice, some bowler prefer to bowl fast (up to 100mph and more which is 160kmph and up), while other bowler try to give their ball more spin which slows down the ball but makes it more difficult for the striker to calculate where to hit the ball.
During the delivery the bowler runs up to a mark which he made before starting with the bowling. Usually the mark is two jumps in front of the wicket. One jump, for the reaction time as the bowler is running on fast. The second jump will be the actual jump the bowler is doing to get out the last amount of energy. In this jump, the bowler turns his stronger leg, so he stands sidewise with the wicket. Then he kicks up is weaker leg and puts all his power on this leg, releasing the ball straight in front of him.
It is important that he does not cross the bowling crease.
Notice, during the whole process of bowling, the bowler does not cock his elbow, otherwise it will be declared as throwing which is after the cricket rules illegal. Therefore the bowler brings all his energy from the shoulder and the power he got through the run up.
He is not required to let the ball bounce the ground, but most of the bowlers do so as it gives the ball more movement and makes it harder to hit. It even can be said that if the ball doesn’t bounce on the pitch, that happened accidentally, because these balls are easy targets for the batsman. As the bowler is not required to hit the ground, there is also no point on the pitch were the ball must or must not hit the ground.