What was the goal of bombing cities and was it successful

Could be for a number of things.

Self defence of a country - defending land, beliefs, religion, for freedom, for rights, for revenge.

If successful then could win them land, defend their country, belief etc (same as above).

If you mean like world war 1 and 2, then it was to take out the most people. Thats why people moved to the countryside to avoid the bombs in the cities.