A laptop is a personal computer designed for mobile use it’s small and lights enough to sit on a person’s lap while in 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 track pad, and/or a pointing stick), speakers, and often including a battery, into a single small and light unit. The rechargeable battery (if present) is charged from an AC adapter and typically stores enough energy to run the laptop for two to three hours in its initial state, depending on the configuration and power management of the computer.

Laptops were originally considered to be "a small niche market" and were thought suitable mostly for "specialized field applications" such as "the military, the Internal Revenue Service, accountants and sales representatives". But today, there are already more laptops than desktops in businesses, and laptops are becoming obligatory for student use and more popular for general use. In 2008 more laptops than desktops were sold in the US and it has been predicted that the same milestone will be reached in the worldwide market as soon as late 2009. 

A size comparison of 3.5” and 2.5” hard disk drives removable media drives – A DVD/CD reader/writer drive is typically standard. CD drives are becoming rare, while Blu-Ray is becoming more common on notebooks. Many ultra portables and netbooks either move the removable media drive into the docking station or exclude it altogether.

Internal storage, laptop hard disks are physically smaller—2.5 inches (64 mm) or 1.8 inches (46 mm) —compared to desktop 3.5 inches (89 mm) drives. Some newer laptops (usually ultra portables) employ more expensive, but faster, lighter and power-efficient flash memory based SSDs  instead. Currently, 250 to 500 GB sizes are common for laptop hard disks (64 to 256 GB for SSDs).  

Some laptop components (optical drives, hard drives, memory and internal expansion cards) are relatively standardized, and it is possible to upgrade or replace them in many laptops as long as the new part is of the same type. Depending on the manufacturer and model, a laptop may range from having several standard, easily customizable and upgradeable parts to a proprietary design that cannot be reconfigured at all.

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Laptops are prized targets for theft. The cost of the stolen business or personal data and of the resulting problems (identity theft, credit card fraud, breach of privacy laws) can be many times the value of the stolen laptop itself. Therefore, both physical protection of laptops and the safeguarding of data contained on them are of the highest importance.