Questions about AMC

I recently heard about the AMC and I was wondering
What is it other than a test?
When is it?
How do I participate?
What math skills do I have to know?
Where can I practice for it (specific websites and whatnot)?

You can find info about the test format and test dates here:

http://www.maa.org/math-competitions

You can also participate in this forum to prepare:

http://www.artofproblemsolving.com/community

http://www.maa.org/math-competitions/about-amc

http://www.artofproblemsolving.com/

Thank you, is there a difference between AMC 10/12 A and AMC 10/12 B?

AMC 10 is easier than AMC 12. Only students in grade 10 or below can participate in AMC 10.

The A and B denote the test dates (sessions). There are 2 test dates each year for each test. IIRC you can participate in either session for each level. For example you can take AMC10 A then take AMC12 B two weeks later.

thank you