'iPad' sounds like just one thing, but Apple has two distinct iPad lines - full-size and mini - and two distinct generations - new and old - available for sale right now. There's the brand new iPad Air and Retina iPad mini, and there's the held-over iPad 2 and iPad mini. But what's the real differences between all these iPads? Does more money really get you more features, does saving up-front cost you in the long run, and how much tablet do you really need? If you're looking to get your first iPad, or looking to get one for family or friends, figuring it all out can be confusing. Here's what you need to know!