Let's take a look at iPad first, it has:

•        7 inch IPS screen

•        Great user experience on user interface

•        Sensible and accurate multi touch

•        Pretty thin (compare to some other tablets)

•        Start from standby mode, less than 1 second waiting

•        10 hours using time

•        Tons of apps that you can choose from app store

The iPad is of course from Apple.   Apple owns, develops, designs, markets and controls all aspects of the iPad and the iPad operating system (iOs).  Because of this, you can use one iPad for a while, accidently break it, buy another iPad, synch all of your exist data and apps with your current iPad and be up and running again.  The same is true for upgrades.  Apple wants you to continue buying their products so upgrading to the newest product is as easy as registering and synching.  

iPad, iPad2 and eventually the iPad3 are still the market's key drivers for tablets. 

Now let's take a look at android tablet:

•    It's open, anyone can produce it, lots more choice for customer

•    There's more ways to play with the desktop, and also you can add widgets like whether, news, Facebook, twitter to check the latest news

•    You can directly manage all data as long as you know how to use copy and paste

•    Support USB/ card reader/ web cam/Wi-Fi, basically it could have some things which iPads don't have yet

•    Support Flash

•    Much cheaper than iPad!!!

However, android is open source software.  That means it is available to anyone to use and modify.  That is one of the reasons android tablets are much less expensive.  One drawback to open source is there's not been a standard protocol yet which means different manufactures produce different apps that they might not compile to each other.  If you have one android tablet just the way you want it and it breaks, the next one you get may not be compatible with the old apps you had.

From user experience side, the iPad is very polished and when you buy one you know exactly what you are getting.  Android tablets are making great strides in becoming polished.  With powerhouses like Samsung and Amazon investing money in the Galaxy tab and Kindle Fire, the android tablets are making ground on the ipads.  For what they lack in polish, they more than make up for in price.

Iphone vs Smartphone:

As with the Ipad and Android Tablets, the Iphone uses IOs and most smart phones use Android.  Both Smartphones and Iphones are like small computers in some of the things they can do.  They both can connect to the internet, have cameras front and rear, play music and videos, access tons of apps.  The major difference is when you go to the apple store and say can I see an iPhone, they show you an IPhone.  When you go to any other phone retailer and say can I see a smart phone, they show you about 20 different phones in multiple colors for every service carrier they have.