enhance ability与improve ability

enhance ability与improve ability
两者有不一样的地方吗?
什么时候应该用enhance 而 什么时候应该用improve?

Please do not understand English in Chinese.
To enhance means to make higher.To enhance my ability means to go to a higher level.To improve means to make better for a profit.To improve my ability means to do something that will gain me something.
If you want your ability to be better for yourself,you enhance your ability.If you want to do better in a test,you improve your ability.
Good luck.