A portable computer is a computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 that is designed to be moved from one place to another and includes a display and keyboard. Portable computers, by their nature, are generally microcomputer

Microcomputer

A microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...

s. Portable computers, because of their size, are also commonly known as 'Lunchbox' or 'Luggable' computers. They can also be called a 'Portable Workstation' or 'Portable PC'.

The principal advantage of a portable computer versus a laptop

Laptop

A laptop, also called a notebook, is a personal computer for mobile use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device and speakers into a single unit...

or other mobile computer

Mobile computing

Mobile computing is a form of human–computer interaction by which a computer is expected to be transported during normal usage. Mobile computing has three aspects: mobile communication, mobile hardware, and mobile software...

is the use of standard motherboard

Motherboard

In personal computers, a motherboard is the central printed circuit board in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple...

s or backplane

Backplane

A backplane is a group of connectors connected in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors forming a computer bus. It is used as a backbone to connect several printed circuit boards together to make up a complete...

s providing plug-in slots for add-in cards.