Barry's answer is correct but a bit incomplete. What he left out is that Spotlight is buggy and tends to 'lose track' of file types. Since Other is everything else, when Spotlight loses what kind of file it is looking it, it becomes Other. While Spotlight isn't good (over time) at identifying how much space is devoted to a specific file type, it is usually accurate about total drive space in use.
To rebuilt the Spotlight database follow these instructions: http://support.apple.com/en-us/HT201716
If the report doesn't change try this terminal method: https://www.techradar.com/how-to/computing/apple/terminal-101-rebuild-the-spotli ght-index-on-the-fly-1305684
Since the "Other" files can be anything, looking for the "Other" is a waste of time. But we do know that the files most likely to be taking up lots of space are media files which are in the Pictures, Movies, and Music folders.