On a Hyundai, TCS stands for Traction Control System. Every time you start the car, the light will come on for a 3 second "bulb check" and then go off. It will also come on and stay on whenever you press the traction control defeat switch (might be labelled "TCS off" or "traction control".) The TCS light will temporarily blink when you accelerate swiftly, especially on sand or snow, as the system regulates traction to prevent wheelspin. This is entirely normal. THis light should go out again once you stop driving in a way that could cause wheelspin.
But if the light is on steady and never goes out no matter what you do, you probably have a fault in the system. I would not be surprised if the ABS light was on at the same time, because those systems share certain important parts, like sensors and other electronics. A dealer visit might be in order, especially if ABS is also affected.