ffmpeg arguments used for converting to mp4
ffmpeg duplicates syntax. Except for the values used, and that the first command set the sampling rate instead of using the default, the commands are effectively the same:

 -loglevel panic  - merely makes ffmpeg less noisy in the shell
 -vcodec copy     = -c:v copy
 -acodec copy     = -c:a copy   # unlisted in the command, but listing here to show there is consistency
 -ab              = -b:a


Note: The other answer info is correct. 

There is a guide online; it lists what every possible argument means.