4 Hard Disk volumes?

EmyPuscas wrote:

...What does the "other volumes" mean? Is it the old OS? macOS 10?...

Could I remove that volume and win back all that space?

https://discussions.apple.com/content/attachment/9392e43f-2879-4180-97ec-e9ff0d932e5c

"Other volumes" refers to any additional volumes that share the storage capacity of that drive device.

A typical macOS installation of Catalina or newer will have five or six volumes within a single container and sharing the total storage capacity of the drive. The APFS volumes are dynamic and may each use more or less space as required by the files that are stored within. The OS manages that without your help.

This is a peek at the internal drive on my Mac using the Terminal command diskutil list

Mine is a 1 TB drive with a single container, and within that container are the five APFS volumes that share the storage space.

If you remove your volume "MAC", then yes, you would recover whatever space is being used, but lose whatever files are stored there, so you'll want to check the contents in Finder to know if there's data that you want to keep.

If each of those untitled volumes has a similar Used capacity of ~770 KB, then it appears that they are empty and, yes, are candidates for deletion.

Please see: Add, delete, or erase APFS volumes in Disk Utility on Mac - Apple Support