Categories:

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. 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 (such as the OQO Model 02) are designed with a miniature physical keyboard (a thumbboard) and mouse interface. They house lower performing, power-saving components (in comparison to larger laptops). Examples of UMPCs are the OQO Model 02 and the Sony VAIO UX Micro PC.
Ultraportables
Laptops with screens typically less than 12 inches diagonally and a weight of less than 3-5 lbs. 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.

A Sony VAIO FJ76 Notebook
Thin-and-lights
Laptops usually weighing in between 4-6 lbs with a screen size of between 12 and 14 inches diagonally. Examples of this variety: the Sony VAIO CR , HP Pavilion DV2000,XPS M1210 and XPS M1330,and Apple MacBook .
Mainstream
Laptops weighing in between 5 and 7 lbs,with a screen size of 14.1 inches and 15.4 inches.Examples:Dell Inspiron E1405, E1505,1420,1520/1521 and 1501, Acer Aspire 5520, 5920
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. 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. These notebooks possess similar features as desktop computers.An example of this is the Dell Inspiron E1705,1720/1721, XPS 1710, 2010, Sony AR, Acer Aspire 7720 and Apple MacBook Pro.

Related devices
Laptops can be understood as a particular point on the continuum of more or less portable computing devices: the point at which the device is large enough to use substantially the same software as a desktop machine, but small enough to support Mobile computing. Other points on the continuum include:
Transportables, also called portable computers
Computers which can easily be moved from place to place, but cannot be used while in transit, usually because they require AC power. The most famous example is the Osborne 1. A transportable, like a laptop, can run desktop software; but it does not support mobile computing.
Tablets
Computers shaped like slates or (paper) notebooks, with touchscreen interfaces include a magnetized stylus and software for allowing input to be recognized by the touch screen. As of 2007, the most common subcategory is the Tablet PC, which is essentially a laptop with a touchscreen. Some tablets have no keyboard; others, called "convertibles", have a screes which can be rotated 180 degrees and folded on top of the keyboard. Tablets may have limited functionality in certain applications that require an actual physical keyboard for typing, but are otherwise capable of carrying out most tasks that an ordinary laptop would be able to perform.
Internet tablets
Internet appliances in tablet form. An internet tablet supports mobile computing, Internet tablets usually use linux and theyre able to run some applications but they cant replace a computer, Internet tablet feature a MP3,Video, Internet Browser, Chat, and picture viewer
Personal digital assistants (PDAs)
Small computers, usually pocket-sized, usually with limited functionality. A PDA supports mobile computing, but almost never runs any desktop software.
Handheld computers
A high-end PDA or small tablet.
Smartphone
A handheld or PDA with an integrated cellphone.
As will be clear, these categories are blurry at times. For example, the OQO UPC is a PDA-sized Tablet PC; the Apple eMate had the clamshell form factor of a laptop, but ran PDA software. The HP Omnibook line of laptops included some devices small enough to be called handheld computers.they are very good. The hardware of the Nokia 770 Internet tablet is essentially the same as that of a PDA such as the Zaurus 6000; the only reason it's not called a PDA is that it doesn't have PIM software. On the other hand, both the 770 and the Zaurus can run some desktop Linux software, usually with modifications.