Telix was a very popular DOS program, distributed as shareware, which acted as a terminal emulator over modems. It could emulate vt100, vt52, ansi, and a dozen or so more obscure terminals. Many people used telix to dial into BBSs, or connect to a un*x shell account where they would read their email, surf the net with lynx or gopher, read news, download files with ftp, write and compile programs, etc.