From SC2Pod
The SCV is the most basic of the Terran units. SCVs perform all manual labor such as the constructing and repairing of buildings, as well as mining both gas and mineral resources. SCVs construct all the Terran buildings. Only one SCV is able to construct a building at a time.
Lore
Initially used during the reconstruction of the Tarsonian Orbital Platforms, the T-280 SCV (Space Construction Vehicle) became a staple in intra-Colonial construction and engineering due to its ability to perform any number of construction tasks within the vacuum of space. It is this versatility, and an unmatched reliability, that make the SCV an invaluable tool in rapidly establishing Marine encampments and strike bases on any terrain. Maintain your civilian status while serving your Colony!
Constructs
Basic Structures
Advanced Structures
Weapons
Abilities
Upgrades
StarCraft 2
The SCV's StarCraft 2 model
The SCV is in the sequel with a few improvements. Most importantly, StarCraft 2 SCVs have an auto-mine capability, meaning that the player no longer has to manually send every SCV towards minerals or gas. Also, SCVs (and all workers) have much improved pathfinding AI. This has resulted in resource gathering being toned down in order to maintain a comparable flow of income. Lastly, as in WarCraft 3, there will be a GUI notification that alerts the player to any idle SCVs.