rm RealNetworks, an internet streaming Media Company, is credited as the developers and owners of the proprietary RealMedia multimedia container format. The filename extension .rm refers to this format which is used as an audio and video wrapper to distribute digital media content over the internet. The first version of this container was released in 1997 and has been popularized for its ability to unpack the digital stream while it is being downloaded over computer networks such as the internet. The format is platform agnostic and works equally well on Microsoft Windows as it does on Linux or Mac OS.
asf The .asf filename extension refers to the Microsoft owned audio and digital video container, advanced systems format. It is a container for windows media audio and windows media video but shares the same internal structure as both WMA and WMV file formats. The format was designed with the goal of increasing efficiency in distribution of audio video files across computer networks. However, it works just as well for local system playback. The asf format forms part of Microsoft's Foundation framework. The major feature of the format is its ability to add digital rights management by providing the framework for encrypting audio and video files.