As a little addition to what Tom said: you are seeing this because you have “Documents and Desktop in iCloud”. It’s very easy to activate this without realizing what you are doing. I am sure that many users have done so and are totally oblivious to it. Do you WANT to store your Desktop and Documents folders in iCloud?
There can be good reasons to do it, but also good reasons not to. Do you need to easily share that data with other macs you have? Do you realize that you probably have way more than 5GB to store (5GB is what you get for free, and just a single video can easily top that, let alone everything else you may have)?
It is a sad thing that a lot of people have no idea of how data is stored and, specifically, what a file system is. The iPhone, despite its huge merits, has ushered in an era of blatant illiteracy in this regard. 🥲