Samsung galaxy s2 sim card type

[kathiny]

I was thinking of getting a samsung galaxy s2 but was wondering what type of sim card it uses? I've had the same sim card for years and I really would like to keep it if I can because it has a good tarrif? Is that what it's called when you get so many text, phonecalls and wap for a set price each month ? Sorry I'm soo clueless with this type of stuff. Thanks for any help given