How does the data plan for the internet access for iPhone 4S work exactly?

I'm going 4S soon (don't care about the 5) and I know that when it comes to when you can access the internet (Safari), you can only access a certain of pages at a time. If I went with the 2 GB data plan then it said somewhere around 100 pages. Does that mean 100 pages per day or 100 pages per month? Also, I was told by a rep.of Verizon that if I'm accessing the Internet using a Wi-Fi connection instead of 3G or 4G or whatever its called, then it won't count towards the data plan at all. Now what if I wanted to access Facebook or Twitter on it? If I used the social networking apps on it instead of Safari, would that count towards my data plan along with using Safari with 3G connection? Please answer my questions because I can't seem to find an answer anywhere.

Yes, anything that accesses the internet using 3G or 4G will count against your data allowance. When you're using Wi-Fi it doesn't count. Movies are the worst bandwidth hogs. 2GB is quite a lot and should cover at least 100 pages a day, but you may want to monitor your usage to make sure you don't go over your limit.