But the graphical representation is not straight forward. The "system" amount can also include the Library, user library and other files. Pictures can also be images in the system and applications. Nothing is straighr forward in that graph.
The Other category is a potpourri of files which include:
• System temporary files
• macOS system folders
• Archives and disk images (.zip, .iso, etc. - often found in the Downloads folder)
• Personal user data
• Files from the user’s library (Application Support, iCloud files, screensavers, etc.)
• Cache files
• Fonts, plugins, extensions
• Other files that are not recognized by a Spotlight search
• Media files that cannot be classified by Spotlight as a media file because they are located inside of a package
They can be located anywhere on your hard drive. The files that you have control over are located in the Applications, Documents, Downloads, Pictures, Music and Movies folders.
NOTE: you can empty the Downloads folder after the apps and/or updates that were downloaded have been installed or applied. Many users have found a couple of Gigabytes of files in their Downloads folder which are no longer needed.
The Info pane for any file, folder or volume is the most accurate method of determining size.