Your processors and graphics chips and other components in your computer can overheat if your system is not properly ventilated. Most PCs come today with a fan or heat sink for both the processors and graphics chips and possibly for other heat producing components. This is all in addition to the main ventilation/exhaust fan of your system box.
Normally, temperatures should reach no more that around 65 degrees centigrade when your computer is crunching instructions and producing graphics to the max. Overheating can cause computers to freeze up or Windows to fail with all sorts of errors. Make sure your computer's cooling components are sufficient for your configuration and that your power supply can handle your system's power demands.