What does cellular data usage: Current Period?

And Current roaming mean? I havea verison iphone 4 with unlimited calls, texts, and 10 gb of Wi-Fi data, my iphone is only 8gb, my billing cycle restarted the 21st, and said I'm already 20% through, but when I check my phone it says under Current Data Usage, Current Period: 17.5gb! I admit I used the interent a little bit, and facebook and snapchat, and the daily clash of clans check, am I over my Wi-Fi already? I share the Wi-Fi with 3 other people, and the stuff I even do does take much Wi-Fi, it got to the point were I turned off my 3g last night!

It's not "Wi-Fi" data, it's 3g/4g

Any time you use internet without connecting to a Wi-Fi hotspot, you use data.

If you share that internet with other devices (so that computers and such can use your data), then that takes up a LOT of data.

Also any video playing takes a lot of data too.

So stop sharing data.