Internet service providers (ISPs) are companies that provide internet access to homes and businesses.
An ISP may sell access to the internet using its own network infrastructure, or else may be buying access from another provider in order to serve its own customers.
For example, BT is one of the largest ISPs in the UK and owns its own network infrastructure. Many other ISPs pay BT to access its network at the local exchange level in order to deliver services to customers.
Virgin Media (formerly NTL) has its own network used to deliver cable TV services, with internet access piggy-backed on this.
