Tablet PCs are computers contained within a single touchscreen LCD panel. They are designed primarily for media consumption, which means they are capable of displaying media in either landscape or portrait mode with the help of an accelerometer.
Accelerometers are small motion sensors inside the tablet PC that detect the orientation of the device. As the user rotates the tablet PC from landscape to portrait mode, the accelerometer detects this change and causes the tablet PC operating system and software to respond by adjusting the display to match the new orientation.
Different types of media are better viewed in different orientations. For example, holding a tablet PC in landscape mode (horizontally) makes viewing movies and pictures a more pleasant experience, while holding the tablet PC in portrait mode (vertically) offers a better experience for browsing the Internet and reading documents or e-books.
In addition to providing orientation awareness, accelerometers can be used to interact with certain applications and games. By tipping the tablet PC in a certain direction, you may be able to instruct your game character to move in that direction.