RTS stands for "Real Time Strategy", and is a genre and sometimes descriptor of games that involve making strategic decisions in real time. Real time is distinguished from turn based strategy games by the fact that all players in a match are not limited by turns or a set number of moves. A good example of differences could be chess compared a computer game like Starcraft or Total War. In chess, both players take turns moving their pieces one move at a time. In a RTS game, players actively move their units constantly while the enemy players move their own at the same time, and micro management(precise control of units) is an important aspect along with strategy.
In Starhawk, Build n' Battle adds a light RTS element not too much uncommon from other RTS games that involve constructing bases while choosing between different structures. Buildings must be bought with Rift Energy, and will play a large role in strategy and tactics as each building and different upgrades grants additional tools and buffs to help win the game.