Internet Service Provider. The company who provides the internet connection. Like with telephones and other utilities, the ISP will have many tariff plans. Depending on your usage you can choose for bandwidth limited or time limited plans or if you are a heavy internet user you should look at the unlimited plans options. When you connect the internet through your broadband DSL connection or through a modem you are at the first level connecting to the ISP’s network, which will then connect you to a larger network or on to the Internet backbone.