Other is data used by the system that's outside of your direct control.
It typically includes caches, temporary files, virtual memory backing, filesystem snapshots, etc. - not something a typical user would interact with directly. Instead, the OS manages this, deleting old content as necessary if space is needed.
You may see the 'Other...' decrease after a reboot, since many files are flushed at shutdown, and you're not likely to be eating much in the way of virtual memory with no apps open, but it will grow over time.
Suffice to say, the OS manages this, and 'right-sizes' it based on your usage. You don't have any control over it.
The most obvious saving available to you is to turn on iCloud Photos, which will offload much of the 200GB of photos data on your system (assuming you have sufficient iCloud storage space).
You could also do the same with your Documents, although that tends to have more implications to your workflow. Without knowing what you do, and how many of those 178GB of documents you need right now, it's hard to tell if that's practical for you.
At the end of the day, 1TB isn't much nowadays and it might be worth looking into additional storage options.