A ribbon cable is a cable with multiple insulated wires on a single flat plane. It is called a ribbon cable as it resembles a ribbon. Ribbon cables are used in computer peripherals such as printers, hard drives.
Ribbon cables are flexible and hence are suited for application such as dot-matrix printers where the printing head has to move back and forth across the page. Ribbon cables also take up very little space as they are flat and can be accommodated even in cramped locations.
By convention, one end of the cable is marked red. This is to be connected to terminal no. 1 in the connector. One downside of the ribbon cables is that it does not allow flexing in the sideways. The cable can only bend up or down.