Does FaceTime cost anything? How does it work?

I want to FaceTime my girlfriend whom I haven't seen in 3 months and miss very much, we chat occasionally on Facebook or twitter and even talk on the phone using my friends phone(I use my friends phone, you'll know why)

My girlfriend lives in Portugal, she's portuguese and a mutual family friend lives here and let's me use said phone to call her sometimes

I miss her so much and I just want to see her face again:'(

Does FaceTime cost anything? I don't have her phone number on my iphone cus it will cost too much so how does it work? Can an email just work?

You can use Face Time over Wi-Fi with no cost. Both of you must have iPhones or at least a newer iPod. You can use the number or an email address. Preferably the one associated with your and her Apple account. Older model iPhones only work on Wi-Fi, but the newer ones will work on 4g, but it uses cellular data, which can be expensive.

Http://www.apple.com/ios/facetime/

facetime uses data from your plan, unless you connect thru Wi-Fi. Only iphone 5 or higher allows facetime to be used with your data plan.

FaceTime is completely free, it using your internet (or your data if not connected to Wi-Fi). You must link your email to your iphone, and she must do the same as well. Add each other's email's to your contacts and after that you just FaceTime her.

Free just need Wi-Fi

No its already on the iphone and is free even if using internationally, so is imessage.