Today, 40 years ago first public call with a cellphone was made. The cellphone weighed 2,5 pounds (1,1kg) and when it hit the market it would cost you little short of $4,000.
If you are afraid your friends, kids or any other person you are borrowing your iPad to, might delete an app by mistake or even intentionally, you can enable restrictions on individual all of the apps.
If you are getting a vast number of email notifications sent by your Twitter account and they started to annoy you, this is how you disable and manage them.