Can I possibly use my iPhone 5 outside the US if it's contract-free?

Well, I was thinking about getting an iPhone 5 contract-free because I don't feel like paying $109.99 per month since I only earn about $300 a month. So I'm just saving my money up for it. So here's the question, Will I be able to take the phone to other countries? And what else does it do? (the features of Contract-free) Please answer! Thanks!

Added (1). Oh, by the way, I was thinking of using T-Mobile, so yeah.

If the phone is a GSM device (uses a SIM card for account information), you can get it unlocked (if it isn't already) and use it in most other countries.