Strategy games have been around for a while, but they are usually turn based. Think Chess, Checkers or Monopoly. The first strategy games to hit the IBM compatible PC were also turn based.
Command and Conquer (C&C) changed things by making an incredibly compelling real time strategy game. Of course it wasn’t the first RTS. Dune, the battle for Arrakis (DBOA) was the first. But C&C was developed by the same developers as DBOA. DBOA was produced on a licence from the Dune IP, so the developers were constrained by this. C&C was produced directly after, and it gave the developers a chance to implement all the things that the wanted to put into DBOA but couldn’t due to the constraints of the license.
C&C gives the user control of mining resources, soldiers and weapons of either the GDI or NOD forces. The goal is to eliminate all mining resources, soldiers and weapons of the opposing sides. This can be achieved by direct attack, or by purchasing additional units such as engineers that can take over enemy resources.
All of these decisions are made real time while the opposing forces also make decisions in real time. It turns out this is a great and exciting gaming concept.