What are the functions of the F1-F12 keys on a computer keyboard?

It's function is whatever the programmer gives to it, or no function at all - it varies by program.

there is no "all" key on the keyboard

peso sign

The F Lock on a keyboard disables the use of function keys. E.G: F1 F2 F3 etc.

Hold down the Shift button under enter and the "-" key (beside the 0) and it makes _ . Hope it helps.