If you would look at the requests for help at this newsgroup that get
responses, you would see that they are fairly specific about what, why,
and what the poster has done to help himself. I'll give you the
benefit of doubt that you're not a troll or a student wanting us to do
your job for you.
For what reason and for what application? Are you taking a class or
developing a method? How have you already researched the issue?
Google gives 907,000 hits, and the manufacturers of the supplies have a
lot of information available for the asking. The concepts really
aren't that difficult.