The Insulation Displacement Connector refers to the way by which the connection is made with the ribbon cable.
UDC connectors are used to terminate 2-pair STP cable; there is no jack (female end) or plug (male end) as it is neutral and both are identical.
The connector and ribbon cable are placed in position and pressed. The pins on the connector are designed to pierce the insulation on the cable and make contact with the wire conductor.
An Insulation Displacement Connector or Universal Data Connector (IDC or UDC) has two rows of 25 pins on 0.1-inch centers.