Ethernet Multiple Logical Groupings
Different Applications; Different Users

It is possible to set up closed subgroups (green solid lines and pink dotted lines) on switches. A recreational or charter boat could set up one logical network for passenger use, and another restricted to the crew.

At  home, you might want to have a separate logical grouping for sensitive things like file sharing and printing, with a different subgroup that is exposed to the Internet. In fish processing plants and similar facilities, you might have separate groups for processing, accounting, and backup.

Speaking of accessing the wild Internet...