It is a platform which allows developers to launch their games; It helps them save over 30% of distribution cost. Most developers and companies have stopped printing hard copies of their games as digital distribution is so much accessible and feasible.
Valve (Steam's parent origination) has launched several games over the years, Some of these include CS: GO and Half-Life. They revolutionized the gaming industry with the introduction of 3d games FPS games in the late 90s.
Steam has collaborated with HTC to build the next generation of Virtual reality technology. This infographic is a tribute to Valve and demonstrates their development over time.
Infographic by: gaminginmydna.com