ISP
Internet Service Provider , A company that provides its subscribers with Internet access.
Customers have a username and a password and can dial-up or use a cable or DSL line to connect to ISP's network which is connected to the Internet. Your ISP does not need to be your hosting provider, or vice versa.
This generally refers to how you access the internet with your computer. Specifically, it is the company you signed up with and where you "dial in" to connect to the web.
If you have an account with Earthlink, then your ISP will be Earthlink.