Mini DVI is a digital common interface on the later G4 12" PowerBook, on Intel iMacs till 2009 and on the white and black pre-Unibody MacBooks and on Intel Mac minis before they changed the design to Unibody.
Mini DisplayPort is the current digital standard on all current Macs to transfer video to an external display or TV. It has been introduced in 10/2008 with the release of the Unibody MacBook and MacBook Pros and has gradually been adopted on all other Macs.
MDP is capable of transmitting video, and since 2010, audio too. MDP is a miniaturised version of DisplayPort. It is also license free and can support resolutions of up to 2560 x 1600, which Mini DVI and Micro DVI are not able to do.
Since 2011, all Macs come with a Thunderbolt port, which is meant for fast data transfer and also as means to connect to an external display device to mirror or extend the Mac's screen.
To learn more about Thunderbolt (TB) and its compatibility with Mini DisplayPort (MDP): Introducing Thunderbolt
MDP adapters and cables can be bought online from: