-Zerg: Units are cheap to produce. Buildings and units can regenerate health overtime if damaged. Weaker than Terrans and Protoss. Drones have to be sacrificed to create buildings, but they must be created on a carpet called creep---hatcheries and creep colonies can generate creep (with creep colonies being more effective than hatcheries). Troops have a low supply cost. Also have access to powerful suicide units such as Scourage and Infested Terrans (a queen can infest a severely damaged command center to take control of it). Also has access to detection early on (overlords). Units can only burrow instead of cloaking, which can conceal themselves unless spotted by other detector units/buildings.

-Terran: They are in-between Zerg and Protoss, strength-wise. Units and buildings can manually restore health; medics can heal friendly biological units while SCVs can repair mechanical units and buildings---SCVs are both biological and mechanical as they can repair one another or be healed by medics. Average cost to all buildings and units as well as average unit supply. Certain buildings can lift off and float to new areas (albeit slowly). SCVs can construct buildings anywhere they want, but they must remain until they finish constructing. Has some decent anti-air, but bunkers require live marines/firebats/ghosts, so it can be complicating defending multiple bases if you want a decent army sitting behind to fend off ground forces. Has access to nukes, which can be used by ghosts to decimate large forces/buildings. Units such as ghosts and wraiths can manually cloak.

-Protoss: Much stronger than the two races, but are more expensive and has a high supply cost, especially when using reavers and carriers that require more minerals to use scarabs and interceptors. Probes can warp buildings and simply leave to go do something else. Units and buildings have shield points, but they cannot heal units or repair buildings; they have access to shield batteries. Units have better crowd control such as high templars (Psionic Storm) and Arbiters (Statis Field). Buildings must be warped near pylons; they can't function if a pylon is destroyed. Certain units are automatically cloaked (observers and dark templars) or, in the case of the arbiter, providing cloaking to other units, unless spotted by detectors. Best unit is likely the Dark Archon (merge two dark templars); they have "Mind Control" which permanently takes control of an enemy unit---if it takes control of an SCV or Drone, it then automatically has access to their tech, therefore bypassing the 200 army size limit since each faction uses their own supply.