In this article, we are going to talk about the basic stuff about the divx codec, but not only that, we are going also to talk about what codecs actually are and why they are present on pretty much every computer around the world.
Well, the reason why codecs are necessary in today’s world of digital video and audio is that audio and video content takes quite a lot of space if it is done in digital format. Namely, only 5 minutes of video with audio when they are recorded take up about 5 GB of space. Things are even worse when we go HD, with 5 minutes of HD video being as big as 25 GB. Therefore, in the original state, these files are pretty much unusable. IN order to have a movie that would run an hour and a half, you would need terabytes and terabytes of space. Also, transferring these files over the internet would be virtually impossible, or at least extremely time consuming.
That is why video and audio compression was invented. Compression is a complex process which has taken quite some effort from scientists, programmers and mathematicians in order to come up with algorithms that would allow video files to be compressed. Or, encoded. They had a breakthrough when they realized that in the 30 frames that usually go into one second of film, only slight changes actually occur on the screen. Therefore, they developed a way to only keep those differences and to leave the rest to be static, so to say. As a result of this, the size of these files became much smaller.
Now, all of the video files are encoded, or compressed, if you prefer this term. In order for you to be able to watch such content, you will need decoding software 
on your computer or whatever in order to decode it and sort of reverse it. This is what codecs are for. They also serve as tools for encoding, but for us, the more important purpose of theirs is that they are able to decode these files and allow us to see these video files the way they were meant to be seen.
Of course, not all video files are of the same format and the best way to know whether a codec is good is to check what kinds of formats it can encode to and decode from. Divx is one of the best in this field and it can do pretty much any format you think of. As a result of this, it is by far the most popular codec in the world right now and used by the majority of people. It is also the reason why you need to have the divx codec on your computer.