DSL refers to the variety of different types of Digital Subscriber Line protocols; high-speed data transmission protocols that are compatible with regular copper telephone wire. DSL is typically used to provide a continuous, high-speed connection directly to an Internet Service Provider (ISP). There are several different types of DSL (ADSL, SDSL, UADSL, etc.), and many of them make it possible to talk on the telephone and use the Internet at the same time. It is also called High-Speed DSL (HDSL).