Wifi/Internet about the Galaxy S?

[Victoria]

Heey !
I have the Galaxy S phone from T-Mobile and when i got this phone, i did'nt think i would find myself using the interent very much . Which might sound Pathetic since it is a smart phone, but enyways i bought the internet use' rarerly' So, i could only use it a couple times a month. For 3 phones, and unlimmited texting i paid $104.00. When i upgraded the rare use of interent, its only $10 each month, and my bill was $177.00 ??.. But i have went over the limit of interent use that month. Since we've got that out of the way , ** MY QUESTIONS ARE**
* Is it possible to turn on the wifi, so when im at home, i can go Facebook , Youtube, Twitter etc Withouth actually using the Internet? ( 4g )
* Is the Andriod Market going on the Interent??
* Are the Apps Interent?
* Is Zege ( Downloading App) Interent?
Thank you if you can answer these questions<3