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.
3g2 Originally being developed by a Third Generation Partnership Project II, it's used in the third generation mobile phones, 3g2 is basically used as an audio as well as video file format. It is a relatively similar file format to 3gp with some advancements as well as limitations. Specifically, the 3g2 format is for CDMA based mobile phones rather than GSM-based phones, this format is used in fourth generation phones as well. Basically, it is for video viewing, it is also used for transferring photos and videos through the internet. Based on the standards of MPEG-4, it is developed in the light to play the media and to deliver it through the internet connection over high speed.