Can this be a pay-as-you-go phone (newbie to mobiles)?

[Silly Turtle]

When you just buy minutes whenever you want to (no bill, contract, etc.) Can it? It's a Samsung B3310 (unlocked). I'm still not sure what 'unlocked' means. So if you could clarify your terms in your answer, I'd be happy

Here it is:
http://www.amazon.com/Samsung-B3310-Unlocked-Phone-Camera/dp/B0036OR3FW/ref=cm_cr_pr_pb_t

Thanks in advance!