There are 3 Races found in StarCraft: Remastered. Each represents a very different play style as they have access to entirely different units and buildings.
The Terran are the middle of the ground race. They offer both cheap and expensive units, and focus heavily on ranged combat and stealth.
The Terran are the only race that can freely build across the map, with no limitations. They are also the only ones that can repair a building, although it costs Minerals to do so.
Zerg units have a healthy mix of range and melee based units. The primary difference is that Zerg units tend to be much weaker than others, but are also considerably cheaper and easier to build.
Although Zerg buildings can only be built on Creep, they are the only buildings in the game that will passively regenerate health. They are also the only buildings in the game that require a unit to die in order for it to be built.
The advanced Protoss have the most expensive and powerful units in the game. This is balanced by long build times and high resource costs.
The Protoss buildings are a mix of the other two. Although you can’t repair them, they have shields which will automatically regenerate. They also can be built anywhere, so long as you build a Pylon along with it.