Real Player is a commercial streaming audio/video solution. A competitor to WindowsMedia et al. There is a RealPlayer for Linux; alternatively you can get MPlayer and it can link to the RealPlayer libraries and play Real clips with that. They usually have the extension .rm or .ram.

The best news from Real for a while is the announcement of the HelixCommunity:

RealPlayer forced MatthiasDallmeier to reinstall Windows after it highjacked all the default settings.
His fault for using Windows in the first place. ;) Wait - you can use Windows? --AristotlePagaltzis

RealPlayer forced zcat(1) to waste an entire afternoon learning how gnome uses mime-types to associate files with their applications. RealPlayer hijacked all Gnome's mime-types for mp3, wav, au, and a bunch of other formats, introduced new types for RealFlash? and flash2-preview (breaking Macromedia's flash plugin for Mozilla) and set itself as the default player for a bunch of flash games that it was completely incapable of playing. Don't think that you're safe from Real's crap just because you don't run Windows!

!RealOne? is a disgustingly Bloated piece of software - full of features you don't want but Real wants you to use, such as content channels/browsers or whatever. --SimonCrosby

A word of warning - The people that make RealPlayer (and it's latest incarnation RealOne?) have a long history with SpyWare. Any which one version of RealPlayer may send of all sorts of information to, and might install other SpyWare without notifying you. (Comet-cursor, Gator, Bonzi-buddy, etc etc) - use with caution! --MarcelVanDeSteeg

I've never seen RealPlayer install any spy ware short of what it reports to, which is easily turned off. -- CraigBox

Go to this site for excellent details on How to prevent RealPlayer from spying on a windows computer That is if you cannot live without it :) -- TroyOldert