An internet service provider (ISP), also called internet access provider, is a company that gives individuals, businesses, and other organizations access to the internet. ISPs do this by allowing customers to connect to their network using data transmission technologies that are capable of delivering internet protocol (IP) packets. The most common internet connections provided by ISPs include dial up and broadband connections. Dial up internet is typically the most affordable kind since it provides the slowest speed.
There are different kinds of broadband connections with DSL and cable modems being the most common, especially when it comes to household use. Other kinds of broadband connections include Integrated Service Digital Network (ISDN), T-1 and DS-1, wired ethernet, rural broadband, satellite internet, cellular broadband, powerline internet, and wireless internet service providers (WISPs). T-1 and DS-1 connections are typically used for businesses that require really high connection speeds since DS-1 (Tier 1) transmission rates going up to as fast as 1.54 Mbit/s and DS-3 (Tier 3) data transmission rates going up to 44.736 Mbit/s. Even faster than the DS-1 are connections with signals carried by the fiber optic network called Synchronous Optical Networking (SONET). Data transmission rates of optical carriers can reach up to 159.2 Gbit/s. We can expect these figures to go even higher as technology improves.
Aside from the most basic service, that is internet access, ISPs can offer add ons like email accounts, storage space, and even hosting services. The first two add-on services are often given for free.