4G LTE Technology

I have doubt of LTE and it’s specifications.

  1. LTE have TD (TDD) and FD (FDD). What are those? I think it is the Duplex Mode. What are other available modes in LTE?

  2. Then what are cat 0, M1 / M2, NB1 / NB2 ?

What is different of there two?

When I buy a 4G sim is it have TD or FD? What are AT commands to check it?