How NRF52 Secure bootloader works?

Hi All,

I'm new to nRF52.

I'm working on nRF52  PCA10040 board. How want to how the secure bootloader works?

I tried to load application from DFU serial bootloader and I come across bank0 and bank1 concepts in bootloader. what these banks are used for?

Where will be code stores?

Help me to understand softdevice, MBR, Application, Boot loader parameters and MBR parameter sections and how Boot loader parameters and MBR parameter sections updates?

Please help me to understand the concept of DFU serial bootloader, secure bootloader.

Thank you in advance,

Basavanagouda.