The Nikon D200 is a 10.2 megapixel digital single-lens reflex camera

Digital single-lens reflex camera

Most digital single-lens reflex cameras are digital cameras that use a mechanical mirror system and pentaprism to direct light from the lens to an optical viewfinder on the back of the camera....

 that falls between entry-level/midrange DSLR cameras such as the Nikon D40

Nikon D40

The D40 is a now-discontinued Nikon F-mount entry-level digital SLR, announced November 16, 2006. Compared to its predecessor, the D50, the D40 had several features removed, a few added, and a lower price: US$499.95 ESP as of November 2009 with the 18–55 mm G-II kit lens, positioning it as an...

, Nikon D40x, and D80

Nikon D80

The Nikon D80 is a digital single-lens reflex camera model announced by Nikon on August 9th, 2006. The camera shipped the first week of September to US retailers. Considered by many to be an amalgam of design elements of the entry-level D50 and high-end D200 cameras, it occupied the same price...

 and high-end models such as the Nikon D2Hs and D2Xs. It was released by the Nikon Corporation in November 2005. The D200 was succeeded by the D300

Nikon D300

The Nikon D300 is a 12.3-megapixel professional DX format digital single-lens reflex camera that Nikon Corporation announced on 23 August 2007 along with the Nikon D3 FX format camera. It replaced the D200 as Nikon's DX format flagship DSLR...

 in August 2007.
Main advantages over the D40, D40x, D50, D60 and D80 cameras include:

• More robust, metal (magnesium alloy) body incorporating environmental seals
• Better matrix metering than D40, D50, or D80 (more sensor areas and less prone to overexposure)
• Higher image resolution than D50 and D40, 10 MP instead of 6 MP (Note that the D40x and D60 are 10.2 MP)
• 11-point autofocus
  Autofocus
  An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...
  
   system instead of a 3-point system (D40, D40x and D60)
• Advanced continuous autofocus
  Autofocus
  An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...
  
   tracking options
• More straightforward controls; many controls to adjust shooting settings (image quality, ISO, etc.) are directly accessible on the camera without going into the menu system
• Five frames per second continuous shooting
• Larger image buffer
• 4 channel sensor output (faster throughput to support 5frame/s & finer color gradation)
• Dedicated PC (flash) sync plug
• Ability to save RAW images with selectable size and quality JPEGs (the D50 and D70s can only save basic quality JPEGs with RAW images)
• Ability to save uncompressed RAW images
• Ability to meter with pre-AF lenses
• Ability to connect NMEA 0183 compatible GPS
  Global Positioning System
  The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...
  
  
• EN-EL3e battery with precise status reporting
• Optional vertical battery grip
  Battery grip
  A battery grip is an accessory for an SLR/DSLR , which allows the camera to hold multiple batteries to extend the battery life of the camera, and adds a vertical grip with an extra shutter release , facilitating the shooting of portrait photography.It usually attaches to the camera body through the...
  
  
• Optional vertical grip integrated with wireless transmitter

Compared with Nikon's professional cameras, mainly the D2Xs, the D200 lacks an integrated vertical battery grip, longer battery life, and some minor features.