A laptop is a personal computer designed for mobile use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device (a touchpad, also known as a trackpad, and/or a pointing stick) and speakers into a single unit. A laptop is powered by mains electricity via an AC adapter, and can be used away from an outlet using a rechargeable battery. A laptop battery in new condition typically stores enough energy to run the laptop for three to five hours, depending on the computer usage, configuration and power management settings. When the laptop is plugged into the mains, the battery charges, whether or not the computer is running.

Portable computers, originally monochrome CRT-based and developing into the modern laptop, were originally considered to be a small niche market, mostly for specialized field applications such as the military, accountants and sales representatives. As portable computers became smaller, lighter, and cheaper and as screens became larger and of better quality, laptops became very widely used for all purposes.

A notebook is an extremely lightweight personal computer. Notebook computers typically weigh less than 6 pounds and are small enough to fit easily in a briefcase. Aside from size and portability, the principal difference between a notebook computer and a personal computer is the display screen. Notebook computers use a variety of techniques, known as flat-panel technologies, to produce a lightweight and non-bulky display screen.

Netbooks are laptops that are light-weight, economical, energy-efficient and especially suited for wireless communication and Internet access. Hence the name netbook (as "the device excels in web-based computing performance") rather than notebook which pertains to size.

With primary focus given to web browsing and e-mailing, netbooks are intended to rely heavily on the Internet for remote access to web-based applications and are targeted increasingly at cloud computing users who rely on servers and require a less powerful client computer. While the devices range in size from below 5 inches to over 12, most are between 9 and 11 inches (280 mm) and weigh between 0.9 – 1.4 kg (2–3 pounds).

Netbooks are mostly sold with light-weight operating systems such as Linux, Windows XP and Windows 7 Starter edition.

Desktops have the advantage over laptops that the spare parts and extensions tend to be standardized, resulting in lower prices and greater availability. For example, the form factor of the motherboard is standardized, like the ATX form factor. Desktops have several standardized expansion slots, like Conventional PCI or PCI express, while laptops only tend to have one mini PCI slot and one PC card slot (or ExpressCard slot). This means that a desktop can be customized and upgraded to a greater extent than laptops. Procedures for (dis-)assembly of desktops tend to be simple and standardized to a great extent too. This tends not to be the case for laptops, though adding or replacing some parts, like the optical drive, hard disk, and adding an extra memory module is often quite simple.

Another advantage of desktop is, that (apart from environmental concerns) power consumption is not as critical as in laptop computers because the desktop is powered from the wall socket. Desktop computers also provides more space for heat to escape. The two large microprocessor manufacturers Intel and AMD develop special CPUs for mobile computers (i.e. laptops) that consume less power and lower heat, but with lower performance levels.

On the other hand, laptop computers offer portability that desktop systems can not due to their small form factor. Laptops also more commonly integrate wireless technologies like WiFi, Bluetooth and 3G, giving them a broader range of options for connecting to the internet, though this trend is changing as more desktop computers come integrated with wireless.