What does reset iPhone mean?

I was just scrolling down my settings then, I came across this ' reset iPhone ' one. What is that? What will happen if I reset my iphone? Will I loose stuff?

It does as it says. It would clear all the data & settings from the phone.

It means to completely wipe out the phone, you will lose everything unless you save it to your apple account.

It will completely erase your phone, and you'll lose everything on it.

Reset iPhone iPhone whenever you are having simple problems with it: it doesn't join networks it should; you've lost control over icon arrangement; your privacy or location settings are a jumbled mess. For safe and secure use of your new phone, you also need Leo Privacy Guard app, keeps your data plan and battery usage under control easily.