Multimedia.3GP

"A filename extension is a suffix to the name of a computer file applied to indicate the encoding convention (file format) of its contents."

If you have for example a .txt you know that the file is a text and you also can have an idea on which kind of software you will be able to run it.
For example in the case of .TXT you will choose something like notepad.

A file extension 3gp is a file extension mostly used for creation, delivery and playback of multimedia over 3rd generation, high-speed wireless networks.
If your OS is unable to open files with file extension 3gpyou may not have the appropriate program installed and in this case you should run a registry scan.
This file extension is probably very well know by the millions of happy owners of a video-capable cell phone.
Infact the file extension 3gpis the file extension needed to transmit audio/video multimedia files between cell phones and the Internet.
It is based on the MP4 format.
These extensions define compressed files designed for smaller file sizes so video can be supported by mobile phones.
.3gp files can be viewed directly on a mobile phone, sent to another phone or transferred to a home computer