While just about any monitor will work on the Mac, Apple only makes one external screen for use with its computers: the massive 27-inch Apple Thunderbolt Display. At $999, it's not the least expensive screen you can use on your Mac, but it is one of the most capable.
The Thunderbolt Display uses a thin film transistor (TFT) active-matrix liquid crystal display (LCD) with in-plane switching (IPS). It sports a native resolution of 2560 x 1440 pixels, set in a 16:9 aspect ratio. Because of the IPS technology, it has a wide viewing angle of 178 degrees, both horizontal and vertical. Apple measures the Thunderbolt Display's brightness at 375 cd/m2 with a 1000:1 contrast ratio, and a response time of 12 ms.
There's a lot more to the Thunderbolt Display than just the specs of its screen, however. The display makes an excellent accessory to a host Macintosh by incorporating three USB 2.0 ports, a Gigabit Ethernet port, FireWire 800 and another Thunderbolt port, making it incredibly expandable. It also has an integrated MagSafe charging cable, making it an ideal companion for the MacBook Air or MacBook Pro.
Having said that, the Thunderbolt Display made its debut in 2011, and it's showing its age. The Thunderbolt Display uses an older industrial design that mirrors Apple's iMac prior to its 2012 "thin" redesign.
The Thunderbolt Display's USB ports are limited USB 2.0 speeds (480 Mbps), while modern Macs have moved on to the faster USB 3.0 standard (5 gigabits per second) instead. The Thunderbolt in the Thunderbolt display is the original Thunderbolt, limited to 10 Gigabit per second data transfer rate. The 15-inch Retina MacBook Pro and late 2013 Mac Pro have already moved on to Thunderbolt 2, which doubles the transfer rate. The MagSafe adapter built into the Thunderbolt display has been replaced with the wider, thinner MagSafe 2 across Apple's entire laptop line, which means Thunderbolt Display owners need a $10 adapter to get it to work.
Still, until Apple introduces a Thunderbolt 2 Display, this is the only game in town for an Apple-branded display.