This concerns principally additional settings for importation.

As you see, some options are enabled whereas some others are disabled. All depends of course of your input file type.

[1] : this is enabled only for mp4/3gp files. Allows to keep only the track specified by his id during importation. You must have the right id to use this correctly otherwise don't use it.
[2] : to import only the first x seconds of your input file.
[3] : this change the Frame Rate of your Audio or Video file. By default, mp4box uses 25 fps. Note that if you want to modify Frame Rate of mp4 or 3gp files, you must first extract each tracks as raw format then recreate a new file with the appropriate Frame Rate.
[4] : to add a language for your track.
[5] : here you can modify the PAR ratio of your video file. You have the choice between 4 presets (16:9 PAL, 16:9 NTSC, 4:3 PAL, 4:3 NTSC). The last item of the drop down list allows you to set your own ratio.
[6] : option enable only for aac files. You must specify the compatibility for mp4box. Whether your audio stream is HE then choose backward compatible otherwise select backward non compatible.
[7] : whether your file has multitracks, by checking this mp4box will keep only the Audio track.
[8] : same idea but here we keep only the video track.
[9] : option enable only for AVI files. Allows you to remove some n-vops.
[10] : to specify a delay (positive or negative) in milliseconds.
[11] : to avoid desync issues. Not mandatory...
[12] : to have a name for our track. You have the possibility to write this name in the list. To save this trackname or to reuse it later, then you can click on "New" button. Your string adds in the drop down list.
[13] : to add a copyright flag in your track.

Notice that by moving the mouse on Location box on the top on the window, you can grab some infos concerning your track.