The fundamental difference between dialup and broadband connections is the manner in which the connection is made from PC to the Internet.
A dialup service connects to the Internet through a phone line with a maximum speed of 56kbps.
Broadband refers to a connection that has capacity to transmit large amount of data at high speed. Presently a connection having download speeds of 256kbps or more is classified as broadband.
Broadband comes in a number of forms - depending how the data is delivered - for example via cable, satellite and most commonly using a telephone line where as a dialup service always connects to the Internet through a phone line.
While using a dialup connection, we need to pay for a local call every time we dial the Internet. In addition phone line is engaged while we are on the Internet. With a broadband connection, phone line (if existing phone line is used) can still be used while using the Internet and both the phone and the Internet work simultaneously and no dialup costs are incurred. Telecommunication systems were originally built to carry analogue signals. In a dial up connection, modems are used to translate digital into analogue signals and communicating with Internet.