Klinky had most everything right. A more in depth review would be this: Ogg was created by Xiph (opensource company) mainly to store vorbis audio. However, a guy named Tobias created a set of directshow filters which allowed reading/writing of video streams inside the ogg container, which is superior to avi in many ways. For simplicity mostly the people of doom9 tacked ogm onto the end of an ogg file with video and not just audio. ogm is the same as ogg, just a way for windows to play one file in wmp and the other in winamp. Anyway the functionality of the container is like.. infinite, the main advantages to it are:
1. vorbis audio. Multiple vorbis audio streams. and anyone should know that vorbis kicks ass compared to mp3, aac, wma, and much of everything else
2. yeah, built in subtitles. you can mux an srt subtitle file into ogm stuff making it a great way to backup sub&dub anime
3. built in chapter points, making backing up dvds cooler since the chapters are retained.
here's an example of all of the above:
