Help What is this menu for ?

[shiberm]

I was at an event where I had to shutoff my phone, when I went to turn it on I wanted to turn down the ringer volumne before it made any beeps so I held the volume down button in while turning the phone back on.

When I did this my phone started with a totally different menu that includes options like clear storage , fastboot .....

Just wondering what this menu is supposed to be used for ?

 

[cp1]

It's for manually loading updated operating systems, etc onto the phone.

 

[mdonova33]

Thats the bootloader.