If you are seeing something interesting on the iPad screen that you would want to capture. Screenshot is quite useful, especially if you have an error on your device and you want to capture an image so that later you could show it to a support tech and they could assist you in fixing the issue.
1. While you are looking at the screen press Sleep/Wake + Home button and quickly let go of the buttons.
You will see the screen quickly flashes indicating that it has taken the screenshoot. Your capture should now be placed in the Camera Roll album. To view the image go into the album and open it up.
Once you have the image you could email it.