First, the question is, what is a tablet? It needs to satisfy a few conditions below:
• It must be portable, which means you can carry it around, a bulk tablet is not a real tablet
• It is a personal computer—this doesn't mean it runs as fast as laptops or desktops, but it does have a CPU, RAM and hard drive
• It has a touchscreen
The concept was first presented by Microsoft back in 10 years ago, but unfortunately it didn't succeed as it lack of many functions plus it's a little bit too advance, a few operation systems could run on tablet PC, such as windows, linux, meego,olpc, os x, and finally android system.
So if you are in the market trying to get a tablet PC but iPad doesn't do it for you, you may take a look at Android tablet, big names such as Motorola, Sumsung and so on, they products have some features which even iPad doesn't have, and since this market getting popular, there are going to be a lot more tablets coming out in 2011 with better features and cheaper price, so if you can wait, it's worth for waiting.
So next, what is Android system? It is an open-source software stack that first appeared on mobile phone, it was founded in 2003, and then in 2005, it acquired by Google, and then the development accelerated, in 2010, it beat its biggest rival Nokia Symbian and apple mac os(operated on all generations of iPhone) became the world's best selling phone platform, but what make android system different from other system is android system is open source which means a huge number of programmers can write applications freely, about 170,000 apps for android, but for android tablet it just thriving to beat iPad and iPad2, although they currently occupy at least 70% market share of tablet market, but just like the battle on smartphone a year ago, it will probably beyond iPad series in a few years time.