Beta - Terran structures and units. Note marines are called marauders.
The beta version of StarCraft was a total overhaul of the StarCraft alpha, replacing the Warcraft II engine the alpha used with a different engine. The beta version showed up in early 1998. Though this version greatly resembled StarCraft's final release version, there were some differences in names, graphics (e.g. transports the size of capital ships) and terrain. Most units could also attack (e.g. high templar having Psi Assault like Tassadar) and use special attacks. For example, the marine (called the "marauder" in the beta) had a grenade launcher, and the goliath could use a machine gun and a flamethrower as well as fire its missiles against ground targets. Valkyries were also in the Beta, but they were removed and then added again in StarCraft: Brood War.
Beta image showing drones flying