Hey there! Good question! I know that “Other Volumes” actually has some intended volumes needed for the Mac to run as it should, such as the Pre-Boot Volume, VM, and of course the Recovery volume (MAC OS base System), as it’s called.
These are a normal part of the Mac OS, in particular APFS formatted disks, (Introduced in High Sierra or later).
The one you mentioned that doesn’t fit is the disk1s5. If you didn’t purposely create another volume, or know of another volume or partition that has data stored on it, you should be able to remove that volume in Disk Utility by highlighting and pressing the “-“ button by “Volumes”, (If that’s not available while logged in, you may have to boot to recovery mode to do so).
But if it’s storage you’re concerned about, I might look at other avenues of freeing storage, or finding what’s using so much on your main startup disk. I might have some suggestions, but let me, or us know what happens if/when you try removing that volume. For any other volume showing in Disk Utility, or in Terminal, (diskutil list/diskutil apfs list), most likely it’s meant to be there.
Hope that helps. There is documentation on it I’d have to find it though, thanks.
