Troyig88 said:

What is a MKV? I assume it is some kind of format?

Not a format as such but a 'container file' similar to Harmys 'm2ts' files but more versatile. An mkv file can contain videotracks, audiotracks, subtitle files, chapters etc. And each of these tracks within the mkv can be in mutiple formats eg diVx, Xvid, x264, DTS, AC3, SRT, SSA. The beauty of them is that you end up with less clutter on your Harddrive or media server (one file instead of mutiple files). And you can edit tracks later by demuxing and remuxing them from and to the mkv container file.