please tell me about this question

 

It is not; a device takes the current it requires. A fuse or circuit breaker is used to break the circuit in case of a short to ground fault.

 

please tell me about this question

If you really want answers, please qualify your question with a few more details. That is like asking "Why is water wet?".

 

You limit current to keep your electricity bill at a sane level.

 

please tell me about this question

Please ask a better question.

ak

 

Some devices that operate from AC such as light emitting diodes need to have the current limited. The most common reason for current limiting is to protect against damage from excess current in the case of a fault.

 

please tell me about this question

The question contains none of the information needed to allow those who understand to provide a worthwhile answer. So the TS needs to explain what AC current, to what device, and the circumstances of the current flow.
Without more information there is no reason to provide an explanation.