Why do we care about Gas, anyway?

Gas (CO2 and sometimes N2) is a normal ingredient in beer. Gas is also the method we use to push beer from the keg to the glass. The right balance of gases will keep the dissolved gas levels perfect and the wrong balance will damage the beer by changing dissolved gas levels in the beer. Any change in gas levels will affect the flavor and appearance of the beer. The primary concern is gas content change and the key elements at work are pressure and temperature.