A tablet, or tablet PC, is a portable computer that uses a touchscreen as its primary input device. Most tablets are about the same size as a small laptop, between 8 and 13 inches (20 to 33 cm) diagonally. Many tablets, like the Apple iPad and Microsoft Surface, can connect to keyboards and use special styluses in addition to the touchscreen input.
Since tablet computers don't use mice and keyboards as their primary input methods, the user interface of a tablet is different than that of a laptop. For example, instead of double-clicking an icon to launch an application or open a file, you can tap its icon once. You can scroll by dragging a page directly instead of using a scroll bar. When you need to enter text, an on-screen keyboard appears for you to type on.
The touchscreens used by tablets support multitouch input, letting you interact with the tablet using gestures designed for multiple fingers — for example, zooming in on something by spreading two fingers apart or switching between apps by swiping with multiple fingers. Some tablets also support special styluses (like the Apple Pencil or Microsoft Surface Pen), which connect wirelessly and let you select objects on the screen, write text, and draw in apps. However, if you attach an optional keyboard and touchpad to a tablet, you can use it just like you would a laptop.
Some computers, known as "convertible tablets" or "convertible laptops," combine elements of tablets and laptops into a single device. A convertible laptop includes a built-in keyboard and touchpad like any other laptop but also uses a touchscreen display. It can fold open to function as a laptop, but the keyboard can also fold all the way around to the back of the screen. When fully opened, the keyboard and touchpad are disabled, and the convertible laptop functions instead as a tablet.