An internet service provider (ISP) is a company that offers individuals and businesses access to the internet. ISPs connect users to the internet through various technologies, such as fiber optics, cable, or DSL. They may also provide additional services like email accounts, web hosting, and online security. ISPs can be local, regional, or national, and they often offer different plans based on speed and data limits. Some well-known ISPs include Comcast, AT&T, and Verizon. Choosing the right ISP depends on factors like availability, pricing, and the specific needs of the user.