'Clamp' means the count will just stop when the entered limit is reached, 'wrap' means the counter will return to the minimum when the maximum is reached and the other way around.

Mean repeat again?

Yes, I suppose so.

For example, we have a counter with an initial value of 0, an increment of 1 and a minimum of 0 and a maximum of 5 and we set it to 'wrap'.

If you start the counter once, the value will be 1, then if you start it again it will be 2 and so on until the value is 5. When you start the counter once more when the value is 5, the value will be 0 again. After the next start it will be 1 and so on.

Since English is not native tongue, think of the wrap feature as a circle.

I have another question:

where is wrap can useful?

I have no clue. 
I've never used it before.