Quick as possible explanation for Americans unfamiliar with cricket:
Bowling in cricket is like pitching in baseball, except you run in and bowl overarm with a straight arm. You have to make the ball bounce. The bowler is trying to make the batter hit a catch to a fielder, or knock over the stumps (3 wooden poles) behind the batter. The distance between them is 22 yards.
There are generally 2 types of bowler: fast, pace or quick bowlers who run in as fast as they can and bowl the ball straight. International-level players bowl at 85-95mph. Spin bowlers use the fingers or the wrist to put spin on the ball and make it change direction after it bounces. Usually bowl at 50-55mph.
Then there are the "medium" bowlers, who generally combine the disadvantages of both (not as fast as the pace bowlers, but there is also no spin on the ball). They are essentially slower versions of the pace bowlers - 65-75mph.
Dibbly-dobblers can sometimes be useful if they are accurate, but are usually good for smacking all over the field. They are often used as a gamble which quite often backfires, hence the name.