Workers (AKA peons) are the units that mine minerals and vespene gas and construct buildings. They are the drone (zerg), SCV (terran), and probe (protoss). All three types of workers cost 50 minerals to produce.
Workers are fundamental to economic and tech development, as they harvest resources and construct buildings.
Most players spend their starting resources, and the first five or so minutes, training workers. Terran and protoss players typically have at least one command center/nexus training workers and do not stop until the late game; zerg must expand more aggressively and have fewer workers per expansion.
Workers are identical aside from HPs and construction method.
Raids may aim to destroy workers. Workers may augment base defenses in an emergency, using large numbers to partially offset their poor combat value.
Each race's worker unit has a different way of constructing that particular race's buildings.
SCVs must be present during the entire construction of buildings. The constructing SCVs may not be controlled during construction; construction must be completed, paused or cancelled to return control. SCVs may begin construction on most open ground.
Probes lay down warp beacons that result in a building after a period of time. The probe may move to another task after setting the beacon, unlike SCVs and drones. Probes may only set beacons inside the psionic matrix generated by pylons, with the only exceptions being the nexus, assimilator, and the pylon itself.
When the zerg require a new structure, drones are sacrificed in the process of mutating into the desired buildings. With the exception of the hatchery and extractor, drones can only mutate into structures if there is already enough creep to fit the completed building.
Workers return 5 minerals per trip from normal patches, and 7 minerals per trip from rich patches. They return 4 vespene gas per trip. Gas may not be harvested from depleted geysers.
The terran orbital command allows the call-down of MULEs; MULEs are temporary supplemental worker units that may harvest minerals and repair. MULEs harvest 30 minerals per trip from normal and rich patches, but takes three times longer to mine than SCVs; an SCV and MULE may mine at the same patch at once. MULEs have no attack and have a limited lifespan good for approximately nine trips.
Wings of LibertyEdit
In StarCraft II: Wings of Liberty, SCVs can be upgraded to repair faster and multiple SCVs can build a structure faster if they work together.
Heart of the SwarmEdit
In StarCraft II: Heart of the Swarm, passing the cursor over a main or a gas-extracting building will show the number of workers related to it (example: "workers: 8/24" on a hatchery and "workers: 0/3" on an extractor).