Steam is the manufacturer of HalfLife, HalfLife2, Counter-Strike 2, etc.. and you buy a game, and validate it on your steam account, and then you can download the game wherever you want, as long as you have Steam.. that's all I know..
n physical chemistry, and in engineering, steam refers to vaporized water. It is a pure, completely invisible gas (for mist see below). At standard temperature and pressure, pure steam (unmixed with air, but in equilibrium with liquid water) occupies about 1,600 times the volume of an equal mass of liquid water. In the atmosphere, the partial pressure of water is much lower than 1 atm, therefore gaseous water can exist at temperatures much lower than 100 °C (212 °F) (see water vapor and humidity). In common speech, steam most often refers to the white mist that condenses above boiling water as the hot vapor ("steam" in the first sense) mixes with the cooler air. This mist is made of tiny droplets of liquid water, not gaseous water, so it is no longer technically steam. In the spout of a steaming kettle, the spot where there is no condensed water vapor, where there appears to be nothing there, is steam.
