Electrical Power Distribution Board Question

Well.

It that deep enough?

You do not provide us enough information to know what you want explained. I was tempted to joke about the possible things that mcb could mean but the link shows that Google does not initially recognize that this abbreviation has anything to do with a distribution board.

You will do yourself and us a favor if you explain at least some of what you do understand and then if possible some of what you do not know for certain.