First, iPad is NOT a laptop. It's just an oversized iPod Touch. Literally. It uses the exact same software. Wifi is when there is a land-based high speed internet in the building and a wireless router is transmitting the wifi signal within a couple hundred feet (depending on the router). Most people have one of these nowadays and common brands include Linksys, Netgear, and D-Link. 3G is what cell phones use to get on the internet. It comes from whatever cell phone carrier you have (T-Mobile, Sprint, Verizon, AT&T, etc.). 3G on the iPad is just the internet part of the cell phone plan and not the talk part (no minutes/texting plan). For example, most people have talk and text plans on their cell phones, and people with smartphones usually have an add-on internet plan that's usually 3G speed internet. If you think you're going to be using the internet on your iPad in places where there is no wifi available (wifi is available in Starbucks, McDonalds, you house probably, etc), then get the 3G. If you have the cash it might be good to just get the 3G anyways because you might decide to use it down the road. All iPads already have wifi no matter what so you can already use it where any wifi is available.
The highest iPad is $900. For $100 more, just get a Macbook. Any Mac you buy will be overpriced, but once people decide they want a Mac there is usually no turning back, so hope this info helps.
And 3G is not satellite internet. Everything we use is radio based, except for GPS of course.
