Xvid (formerly 'XviD') is a video codec library following the MPEG-4 video coding standard, specifically MPEG-4 Part 2 Advanced Simple Profile (ASP). It uses ASP features such as b-frames, global and quarter pixel motion compensation, lumi masking, trellis quantization, and H.263, MPEG and custom quantization matrices.
Is a format of audio/video data, which is the most popular today. It can contain files encoded by different codecs, but they will be played in sync and create a unified image to the end user. AVI container supports function in multi-threaded mode, and allows different ratios of audio and video codecs.