LAPTOP: A portable computer.
NOTEBOOK: A laptop computer that weighs in a range from five to seven pounds. The term originated when laptops were routinely more than 10 pounds, and those that became lighter were placed in a special "notebook" category. In practice, notebook computer and laptop computer are synonymous.
SUBNOTEBOOK / MINI LAPTOP: Portable laptop computers that weigh less than four pounds may be called a "subnotebook" or "mini laptop." In order to reduce weight, subnotebooks often eliminate built-in CD/DVD drives, relying on external units to be plugged in when needed. However, if optical discs are required on the road, an external drive in the same travel bag as the computer generally results in more overall weight than a built-in drive would have added in the first place.
MINI LAPTOP / NETBOOK. This category of ultra portable, "mini laptop" made its debut in the 2007 time frame. A subnotebook weighing from two to three pounds, mini laptops have screens in the seven to nine inch range and no optical drives. In 2008, Intel coined the term "Netbook" for small "notebook-sized" portables that use its Atom processor (see Netbook).