dial-up modem - Definition from the Hotspot Shield Glossary

This type of internet connection is established using a modem and is not a permanent connection. The modem literally “dials up” to a standard phone line which acts as the method of transferal to receive and send internet data.

The dialing process involves the modem dialing a set telephone number provided by the users ISP (Internet Service provider) that is solely used for creating dial-up connections. Once the number has been dialed, the ISP will attempt to create a connection - You can usually tell this is happening by the strange buzzing sounds that can be heard from the modem. A main issue with the dial-up modem was that if someone else wanted to use the telephone, or if you received an incoming call, your internet connection would be disrupted and ultimately disconnected.