Im New To [No contracts]

[WTF]

I want to leave Verizon for Tmobile. Yes I know coverage is everything but I really need to get my hands on the HD 2. (Coming from Tp1)

How does no contract work exactly. What do I pay after I buy the phone? Do I still pay for data...and other expenses?

[Note] The only thing I understand about not having a contract is being able to switch whenever...correct right?

Thanks guys!!