It is pretty self explanitory...someone who provides internet access.(AOL, MSN, MTCO, TRI-NET, etc...) They are companies who give people the chance to enjoy the internet, pretty much like a huge router.

An Internet service provider (ISP, also called Internet access provider or IAP) is a business or organization that offers users access to the Internet and related services. Many but not all ISPs are telephone companies. They provide services such as Internet transit, domain name registration and hosting, dial-up or DSL access, leased line access and colocation. Internet hosting services run servers, provide managed hosting, and include the Internet connection. Generally, an ISP charges a monthly access fee to the consumer. The consumer then has access to the Internet, although the speed at which this data is transferred varies widely. Internet connection speed can generally be divided into two categories: dialup and broadband. Dialup connections require the use of a phone line, and usually have connections of 56 kbit/s or less. Broadband connections can be either ISDN, Broadband wireless access, Cable modem, DSL, Fiber Optics, Satellite or Ethernet. Broadband is always on (except ISDN that is a circuit switching technology), and varies in speed between 64 Kb and 20 Mb per second or more. With the increasing popularity of file sharing and downloading music and the general demand for faster page loads, higher bandwidth connections are becoming more popular. Hope This Helps, Tiff

A company or other origanisation which provides access to the Internet to businesses and/or consumers. An IAP purchases an Internet link from another company that has a direct link to the Internet and resells portions of that bandwidth to the general public. For example, an IAP may purchase a T1 link (1.544Mb/s) and resell that bandwidth in chunks consisting of ISDN (64Kb/s, 128Kb/s) and analog modems (14.4Kb/s, 28.8Kb/s). The IAP's customer base is likely to include both businesses and individuals. Individual customers usually connect to the IAP via a modem and telephone line to a (preferably local) point of presence. ref.-dictionary.com