What are the files on a Macbook SSD?

Question

macOS

I have a macbook air that has a 128 GB ssd, which is basically enough for me.
But, when I opened the "storage" tab in the "about this mac" section, I saw that 37 gigabytes were occupied under the name "other".
Actually the question is, what are these files and how can they be cleaned?

Answer 1

OS files, any cache, and just undefined files. Let's say mp4 movies will be recognized as movies, but mkv won't.
You can clean it with CleanMyMac

Answer 2

There is a good DaisyDisk program that visually shows all the occupied space on a Mac.