permission that allows a user to have permissions that are similar to those of the file’s group owner
In addition to files, SGID can also be set on directories.
Any subdirectories created in this directory will automatically inherit the SGID permission.
all new files and subdirectories created in this directory will inherit the directory’s group ID, rather than the group ID of the user who created the object.
Note that the SGID permission is not applied to existing objects in the directory, nor is it applied to objects that are moved from other locations into the directory.