How do pay monthly contracts work?

I'm thinkin gof buying a iPhone 4 8gb phone by paying monthly, but how does it work? Do i pay the amount at the end of every month or what? And when it says stuff like 100 mintues what does that mean? That you have 100 minutes per month or what? And how much is 250mb data usage? When i get my iphone i will be using the internet everyday and i will go on websites like facebook and twitter, is 250mb enough?

I'll try go through what I can. In order to get a contract:
* you must be 18 years old
* pass the credit check
* bring valid identification

Now, the way a contract works is you pay a monthly fee, the price of your contract can depend on either the phone you're ordering, the contract length and tariff. You're usually tied into a 24 month contract, you may also have to pay a month or two upfront for your contract.

About your "what does 100 minutes mean", that means you have 100 minutes of call time per month, which is 1 hour and 40 minutes. Not that much.

For your web data: 250mb for everyday use is not something I would recommend. About 1GB+ I'd say would be enough. (in my opinion)

Firstly, a phone contract is when you pay a certain amount a month on to the provider, but you have to pay it for the full contract length - if you want to cancel it you usually either have to return the phone, or pay the rest of the contract upfront - for example, if you had 4 months of your contract left but you wanted to cancel it you would have to pay what you would have paid per month x4.

As for minutes, this is how much allowance you get given by the provider - your phone will add up all your calls, which is based on how many minutes you've used. If you don't call much, this should be fine.

As for MB, if you just want to browse the web every day and go on simple websites such as facebook/twitter then 250mb will be enough. On my contract I use it loads, for background apps too yet I never use more than 250mb. Just use Wi-Fi whenever you can, and don't watch YouTube videos or download apps using it and you should be fine.

However, I wouldn't get the 8gb phone because that really isn't enough space - as soon as you get it around 2gb is already used, so only 6gb is left for your stuff, which isn't that much if you want to use it for music, games and everything. I would suggest a 16gb one.