Video technology has evolved quickly over the last ten years and, to keep pace, Apple has had to change out the video ports on Macs with roughly the same frequency that Lady Gaga changes outfits. The general state of things currently is that older standards like VGA and DVI (and their variants) are being phased out and replaced by HDMI and DisplayPort (including its variants, Mini-DisplayPort and Thunderbolt). There are still plenty of peripherals with the older ports, however, and finding the correct adapter to suit your needs can be tricky.