Notebook or Laptop

A laptop computer, or simply laptop (also notebook computer or notepad), is a small mobile computer, which usually weighs 2-18 pounds (around 1 to 8 kilograms), depending on size, materials, and other factors.
Laptops usually run on a single main battery or from an external AC/DC adapter which can charge the battery while also supplying power to the computer itself. Many computers also have a 3 volt cell to run the clock and other processes in the event of a power failure.
As Personal computers, laptops are capable of the same tasks as a desktop computer, although they are typically less powerful for the same price. They contain components that are similar to their desktop counterparts and perform the same functions, but are miniaturized and optimized for mobile use and efficient power consumption. Laptops usually have liquid crystal displays and most of them use different memory modules for their random access memory (RAM), for instance, SO-DIMM in lieu of the larger DIMMs. In addition to a built-in keyboard, they may utilize a touchpad (also known as a trackpad) or a pointing stick for input, though an external keyboard or mouse can usually be attached.
Terms sometimes used for subtypes of laptop computers include:
UMPCs
These Ultra-Mobile PCs are mobile computers with a size comparable to PDAs - they are extremely portable. They are now officially called notebooks as the term lap- top insinuated the laptop should be used on the lap, this however caused the hard drive to over heat thus in turn can seriously damage the computer. Because of their small size, they incorporate a 20 cm (7 inch) or smaller touch-screen for the user to interact with it (as with a virtual keyboard), though some are designed with a miniature physical keyboard (a thumbboard) and mouse interface. They house lower performing, power-saving components (in comparison to larger laptops).
Ultraportables
Laptops with screens typically less than 12 inches (30 cm) diagonally and a weight of less than 3 to 5 lb (1.4–2.3 kg). Their keyboards are usually not full-size. Their primary audience is usually business travelers, who need small, light laptops. Ultraportables are often very expensive, have extended battery life, house power-saving CPUs and almost always have integrated graphics.
Thin-and-lights
Laptops usually weighing in between 4 and 6 lb (1.8–2.7 kg) with a screen size of between 12 and 14 inches (30–35 cm) diagonally.
Mainstream
Laptops weighing in between 5 and 7 lb (2.3–3.2 kg), with a screen size of 14.1 inches and 15.4 inches (35 and 39 cm).
Desktop replacement computers
Powerful laptops meant to be mainly used in a fixed location and infrequently carried out due to their weight and size; the latter provides more space for powerful components and a big screen, usually measuring 17–20 inches (43–51 cm). Desktop replacements tend to have limited battery life, rarely exceeding three hours, because the hardware is not optimized for efficient power usage. Sometimes called a luggable laptop. An example of a desktop replacement computers are gaming notebooks, which are designed to handle 3D graphic-intensive processing for gamers.