Watching a video or movie on your iPad screen? If you have an AppleTV gizmo attached to your big TV screen, you can see it displayed on your big TV screen via Apple AirPlay.
Double-click your iPad Home Button to see the bottom row of app icons shown above, then scroll to the left-most end of the row to see the buttons above.
When you click the AirPlay button, a window will open, letting you choose where you want to see your movie.
[Addendum: iPad 1 does not mirror everything that can appear on the iPad screen (such as web pages) but you can play many YouTube movies and other videos, sending them to your TV screen using AirPlay. Look for an AirPlay icon on the control bar under your video. If it’s there, you can stream it to AppleTV.]