ball-diff-maintenance

[Lowie]

I have already read lots of posts, discussing the different brands of diff-grease ... but I still wonder about a few things .. as ..

why do you need a different type of grease on the diff-plates and on the thrust-bearing.
Basically, the diff-balls + diffplates, act as a bearing too.
SO why the different greases.

Also I have heard about people using the same grease on both diff-plates & -balls and on the thrust bearing. In this case, it was about a kind of ceramic grease.

Can someone explain me these things and maybe also what the different types of grease are, such as ceramic, silicone, ...?

thx in advance!