DIfference between TARGET and MAXIMUN Bitrate

 Target and Maximum bit rate: these come into play when using encoders that employ variable bit rate (VBR) encoding. Target bit rate--like its name suggests--is the bit rate that you want the encoder to shoot for, and use as a relative average. Maximum bit rate--no points for guessing--is the greatest bit rate that you will let the encoder use in segments (typically in divisions called GOPs or groups of pictures) where there is motion or greater visual complexity (highly detailed patterns, or fog, for example). If the encoder was to run full tilt boogie, the maximum bit rate would determine the size of the file; this is roughly equivalent to using CBR or constant bit rate encoding. However, because you've selected a target bit rate (typically, some modicum below the maximum bit rate), the encoder will do its best to maintain that bit rate or lower throughout the video.