Understanding VBS main/git repo in different environments

Summary:

If we are using the same project, but are publishing to main in different environments, are there multiple mains per each environment or is each main possibly a different version?

Content (please ensure you mask any confidential information):

We are continuing to dive into VBS and have appreciated the many Let's talk tech webinars related to the tool.

During the webinars, there are many pictures related to the structure of VBS and many of these make sense.

One area that I am still working to get my head around is the connection between the different development environments and the main branch.