Steam will let you download games via its online platform with regular sales to entice further game purchases. Problems obviously arise when Steam is down, and this would cause issues for millions of users if the outage continues for hours rather than minutes. Steam is supported on Linux, Mac OS X, and of course Windows.
Is Steam Down for you? We have listed a few support details on this page, in case there is issues, although you can also report any problems and major downtime for their website or online games below.