VGA is an analog standard for video signal transmission, developed by IBM. It can accommodate only a single video signal. VGA is a very popular format used in computer displays.
HDMI is a newer and digital transmission standard; created by a coalition of leading consumer electronic manufacturers. The major difference is that it can carry multiple digital audio channels besides video signal. Today HDMI has become a standard interface in all leading consumer electronic items like TVs, DVD Players, Audio Systems as well as Personal Computers/Notebooks and offers seamless connectivity and signal transfer between devices.