Managing disc space, what is "Other"

The Other category contains anything which does not fit into the other categories listed. It also can include temporary files or other files which your user does not have permission to view.

When you are in the Storage tab of the About This Mac window, if you click on the Manage button it will give you some advanced options to help wrangle the storage utilisation on your Mac.

Apple have a bit more information under support article HT206996 which you may find helpful.

see this article: What is "Other" storage on a Mac, and how can I clean it out? - Apple Community

then see this: How to free up storage space on your Mac

and finally: Find and delete files on your Mac

Apparently, 225 GB are being taken by the 'other' category on my computer and i have tried every thing to delete them.