If you have set a password or restriction code on your iPad, what happens if you forget what your password? If you set a password and turned on the erase feature, after 10 wrong attempts, the iPad erases the data. Even if you don’t set up the erase feature, you are still unable to use your device.
To reset your password or restriction code, follow these instructions from Apple. http://support.apple.com/kb/ht4097
Keep in mind you may loose some data and apps. You can reinstall your purchased apps from the app store.
A piece of advice… back up your iPad regularly.