Drivers ensure that your graphic card is capable of communicating back and forth with the rest of the PC effectively. Making sure your drivers are up-to-date can solve many issues and improve your computer's performance.
The following links contain the most up-to-date drivers for each manufacturer:
Nvidia (GeForce): http://www.nvidia.com/Download/index.aspx?lang=en
AMD (Radeon): http://support.amd.com/fr-fr/download/auto-detect-tool