A zealot is a unit in the game StarCraft, made by Blizzard Entertainment, released in 1996. It is of the Protoss race, as opposed to Terran or Zerg. A zealot stands roughly two meters (six feet) tall. It's weapons consist of two Psion Blades, which inflict Normal-type damage.
They are best used in large groups midway through a game; using hotkeys is essential, as 36 to 60 Zealots are a nearly unstoppable force, even if the enemy has air attackers, because the zealots will wipe out his base, destroying him, more quickly than they can be killed. HP is 100 points, and shielding is 60. Shields are a key part of Protoss strategy. They can be regenerated nearly instantaneously with the aid of a Shield Battery. Building a Shield Battery near an enemy's base can help you win a decicive victory.
Zealots start out with 1 point in Armor and can be upgraded to 4. Their "swords" start at 16 damage and can be upgraded to 22. Their unit size is medium, which means four can fit in a dropship (a flying transport). Medium size also means that explosive weapons (such as a Terran Siege Tank attack) will only do half damage. This, as well as the fact that a Zealot is a melee unit, where atank is ranged, makes the Zealot the best Protoss ground attacker against tanks. A tank that it in "Siege Mode" takes roughly four seconds (depending on game speed) to be able to hit a melee-ing zealot.
Perhaps the two most important things about Zealots are their build speed and their run speed upgrade. Zealots take a mere forty seconds to build, the second shortest of the Protoss arsenal. This allows you to build up a dozen Zealots relatively quickly, which is important to help protect the Photon Cannons that are so important to the protection of a Protoss base. The movement/attack speed increase is unique to the Zealots and the Zerg Ultralisks. (Oneiromancer points out that Zerglings also get movement/attack boosts, but that requires two upgrades as opposed to one. Terran Marines also can get a boost, but it requires Stim Packs, which will eat 10 HP per Marine.) This makes them travel much faster across the map, ideal for catching and killing other units, or for storming an enemy base.