The Protoss own the strongest units in Starcraft.  These tough units, however, also take the longest to make.  The Protoss are always at severe risk of being rushed against with the zerg.  Consequently, they are generally preferred in games where rushing is not allowed.  The Protoss's shields recharge and can bring a unit up to partial strength even after a very close encounter with death.  The Protoss also have a wide array of special abilities.  Unfortunately, most of them are not available until much later in the game.  The Arbiter will always cloak any unit within it's range.  The Arbiter can also immediately transport any unit within a certain area to it's current location via it's Recall ability.  The Arbiter can also freeze units with it's Stasis ability.  These units also become invincible, however, so all you are doing when you use the ability is holding them off until you can get some forces in to destroy the frozen units.  The Templar can use Psionic Storm to weaken enemy units.  Two templar can morph together to get an Archon, a rather formidable foe.  Dark Templar are permanently cloaked and very powerful.  They come in handy when you enemy has no detector units to counter them with.  Two Dark Templar can morph together to give you a Dark Archon.  Dark Archon have their own array of Abilities, the most noticable of which is Mind control.  They can turn a single Enemy unit into your own unit, even if that unit belongs to another race.  Click on some of the links below to find more detailed information about the Protoss.