Cortex-M3 Registers

Hello guys.

I am studying the Cortex-M3 technical reference manual.

I have some doubts:
- What is the function of each of the 13 general purpose 32-bit registers, R0 to R12?
- What does Link Register (LR) do?
- What is the function of the xPSR register?
- What does the DebugReturnAdress() register do?
- What is the function of CONTROL, FAULTMASK, BASEPRI, PRIMASK of register 5b10100?

Thank you in advance!