Low power mode

It is meant to save the battery. See this link...

Use Low Power Mode to save battery life on your iPhone - Apple Support

Please click on the link I provided. It will answer your question.

wael_salemm wrote:

So it is not affect the battery ?

It will make it last longer.

That appears to be the general idea!

frazzm737 wrote:

That appears to be the general idea!

Yup. Sometimes people just need to hear it a couple of times before they believe. ;-)