Zealots are the basic unit used for the protoss throughout the StarCraft universe. They sport 2 enegy blades placed on the sides of their arms and attack by thrusting their arms at their enemies. Zealots are also considered to be regular protoss civilians.
 Game Usage
 Protoss vs Terran
Zealots are not used until their speed upgrade is researched. Initially slower than a Dragoon, they become easy pray for the Vulture. With the speed upgrade, Zealots are used to confront Tanks.
 Protoss vs Zerg
Zealots are most effective against Zerglings and Hydralisks, especially with speed upgrade and attack upgrades. If Protoss has 1 attack upgrade higher than Zerg's armor, Zealots kill Zerglings in 2 hits rather than 3. However, Lurkers can take care of Zealots fairly easily with their splash.
 Protoss vs Protoss
Just like PvT, Zealots are not used often until speed upgrade is researched. In the later stages, Zealots are often used as 'meat shields' in Zealot/Dragoon/Archon/High Templar army clashes, with Dragoons and High Templar in the back.