A dial-up connection is the most affordable but slowest internet connection, and it uses a regular phone line connected to a modem.
Dial-up is established when a device uses PSTN (public switched telephone network) to connect to ISP (Internet service provider).
Dial-up is still used in remote or less populated areas in which establishing other types of connection is complex.
In these cases, ISPs often provide users with free dial-up connections.