IPhone 5 Internet usage HELP please?

[hope]

Hi there. Got my iPhone today and I am on a unlimited plan however I have 2GB per month of Internet but I have no idea how much in terms of hours that is? Also, I have free apps such as Facebook, tumblr and twitter. When I exit these I never usually log out because its too much aggravation. I just wondered with me leaving these on 'standby' does it eat up all my Internet usage continuously or does it only count when I'm actually using them? Thank you for your time.

[Tweaker296]

They won't use up usage unless you leave the browser open

[X_Men_First_Ass]

Just go to settings, general, usage, cellular usage. That will tell you how much you've used already.

Loading a yahoo answer page using the mobile version takes up about 20 to 50 kb.

As long as you're near a wifi spot, nothing to worry about.

Facebook, etc. will not use data unless you tell it to fetch. Fetch just means that it will check periodically to see if you have anything new.