Beginning in 2005, Apple released several computers with a Mini-DVI port, including the 12-inch PowerBook G4, Intel-based iMac, the MacBook Intel-based laptop, the Intel-based Xserve, the 2009 Mac mini, and some late model eMacs.
The port was only used until 2008 when it was replaced with the Mini DisplayPort. The port is used instead of a full-size DVI connector to save physical space while allowing the computer to be connected to a DVI-D display.
When the original Mac Pro was released in 2006, it included two side-by-side DVI-D connectors (Digital Visual Interface) on the back so two DVI displays could be connected at the same time.
Since the ports were close together, Apple shipped this DVI-D Male to DVI-D Female Cable Adapter in the event that the cable interface of the display was too wide to fit the connectors from both displays. The adapter’s function is to extend the port an extra six inches from the computer.