Hey guys!

Well im pretty new in this. So would like to seek some advice/clarification with regards to the two Micro Controller(MC) onboard my APM 2.5. 

Below are some of my queries:

1) Why is there a need for two MC.

2) Differences in their function.

3) Output from onboard sensors could be drawn out from which of the MC.

Any help would be appreciated as I am currently doing a solo project for my undergrad studies. Thanks!