Elements of a basic RTS?

Solution 1:

A strategy game needs:

• a map/board
• units
• those need to have strengths and weaknesses

To add some diversity:

• economy/resources
• upgrades (like +armor/+attack)
• technology tree to unlock stronger units/skills/upgrades
• restrict knowledge about the opponent (Fog of War)

And to be real-time:

• simultaneous actions from the opponents
• need for time-management

Why we need all this?

Without a map, how would you make contact with your opponent? Obvious! We need a battlefield. Since you need some way to beat your opponent you need forces (named units). And with them come the first strategic components: some units "counter" other units, and to be successful you need an effective army which is in some way better than the one of your enemy.
But if the players had their army from start, the outcome would only be determined by control and execution and the whole thing is a tactic-game. This is where economy and resources kick in: these are gathered by special units, often simply named workers, which could be woodcutters, stonemasons and food-gatherer or SCVs and drones - totally depending of the games setting. In most games there is more than only one kind of resource available. For example, in Starcraft there are Minerals and Vespine Gas: Minerals are basis for simple structures and units, whereas vespene gas is needed for more advanced technologies and units and upgrades. This concept can also be seen in WarCraft with gold and wood. With gathered resources the player gains the ability to create more structures, e.g.

• unit production facilities like barracks or factories
• technology buildings like academies or technology-labs
• upgrade buildings like forges or workshops
• defensive structures

These resources are needed to produce units and buy upgrades for them. Resources are also limited in some way limited, which adds one strategic goal: starve out your opponent in some way where he has no more income and cannot produce more stuff. Maybe there sometimes comes a moment when all resources are used up or only some are left and the both factions fight for them.

not done yet, but I wanted to show that I'm working on it ;)

Solution 2:

Lazyweb answer: http://en.wikipedia.org/wiki/Real-time_strategy

Excerpt copy/pasted here:

Real-time strategy (RTS) is a sub-genre of strategy video game which does not progress incrementally in turns. Brett Sperry is credited with coining the term to market Dune II.

In a RTS, as in other wargames, the participants position and maneuver units and structures under their control to secure areas of the map and/or destroy their opponents' assets. In a typical RTS, it is possible to create additional units and structures during the course of a game. This is generally limited by a requirement to expend accumulated resources. These resources are in turn garnered by controlling special points on the map and/or possessing certain types of units and structures devoted to this purpose. More specifically, the typical game of the RTS genre features resource gathering, base building, in-game technological development and indirect control of units.