On the original iPad, the only way for teachers or presenters to share what was happening on the tablet’s screen was to mount a camera above it and project the results. (Actually, it’s possible to hack the iPad to get a video-out feed, but that’s a method more appropriate for advanced users.) The iPad 2 can mirror its video to an HDTV, digital projector, or other similar device. All you need is an Apple Digital AV Adapter or Apple VGA Adapter; plug it in and mirroring is automatically enabled.
If you also own an Apple TV, the iPad 2 can mirror its screen over Wi-Fi.