The iPad offers a 9.7-inch touchscreen that employs multi-touch technology. Multi-touch allows users to control items on the screen with more than one finger simultaneously (thus the name). It's multi-touch that enables some of the features made famous on earlier Apple multitouch devices like the iPhone and iPod touch, such as tapping the screen twice to zoom in or "pinching" and dragging your fingers to zoom out.
The iPad comes in two versions, a WiFi-only version and one with an always-on wireless 3G data connection. While the iPad 3G sports a slightly different back (to make room for the 3G antenna), the models are otherwise essentially identical. Both models use sensors like an accelerometer to produce some of their best usability features, but neither offers the ability to increase memory.
To understand the full set of buttons, ports, and switches on both iPad models, read the Anatomy of an the iPad. Other hardware features include:
Screen - A 9.7-inch multitouch screen, oriented vertically. It is not oriented for a 16:9, HDTV-style image, though, so video playback often includes letterboxing bars.
Mute Button - While this button used to be a hardware-based screen orientation lock, as of iOS 4.2, this switch became a volume mute switch, like on the iPhone. The screen orientation lock is now software-based.
Memory - The iPad uses solid state Flash memory to store music.
Camera - Starting with the iPad 2, the iPad offers two digital cameras, one facing the user, one in the back of the iPad. Both cameras can take still images and video, with the video being 720p HD quality.
Since it's built on the iPhone OS, the iPad offers many of the same features as the iPhone and iPod touch, including:
Web browsing - The iPad offers the best, most complete mobile browsing experience. But, just like the iPhone, it doesn't support the standard Flash browser plug in.
Email - The iPad has robust email features and can sync to corporate email servers running Exchange, both of which will be improved by the features added to iPhone OS 4.
Calendar/PDA - The iPad is a personal information manager, too, with calendar, address book, notepad, maps, and related features.
iPod - Like all iPhone OS devices, the iPad's music player features offer all the advantages and coolness of iPods.
Video playback - With its gorgeous 9.7-inch screen, the iPad is a great choice for mobile video playback, whether using the built-in YouTube application, adding your own video, or buying or renting content from the iTunes Store, or using the Netflix or ABC video player apps.
Apps - The iPad's capabilities are made even more compelling thanks to the App Store, which lets users add all kinds of third-party programs, from games (both free and paid) to Facebook and Twitter to restaurant finders and all kinds of other apps.
eBook Reader - Thanks to Apple's iBooks app, as well as third-party apps from Amazon, Barnes & Noble, and others, the iPad is also a terrific ebook reader.