Child Site Question

I’m a real newby, so I’m not even sure ‘child site’ is the right words to use.

What I’s like to have is an overall site specific to an entity or organization, then within that site, be allowed to create child sites for various projects, issues that inherit the parent sites theme, but sort of run independently.

I’ll use what I am thinking of as the example. I have a little farm I bought from my parents that I am cleaning up, restoring, and staring new projects.

So the main site might be ‘Cherry Farm’ and I would choose & customize an agricultural theme for it. This main theme would allow the usual posts, pages, etc generally related to the farm, such as a farm history, contacts, etc.

But then I would like to have a plugin or whatever, that would allow easy creation of project mini sites related to the main site. These mini or child sites would inherit the main theme but have their own admin, main pages, etc. Sort of many wordpress sites within one main site. Example: Listed on the main farm site is project ‘reservoir’ link. Following that link takes you to mini site ‘reservoir’.

Is this possible at all or do I just need to create a site for each project separately?

Thank You