What does DivX mean?

DivX is a brand name for products created by the DivX company. The term is commonly used to refer to the popular DivX codec, which is used to compress long videos to make their file sizes smaller while keeping the video quality relatively high.

A codec is a device or program designed to encode or decode digital data streams: videos streamed over the internet are typically encoded to reduce their sizes for quicker transmission over the internet and then decoded by your computer (using a corresponding codec) so that they can be played back for you.