Hey there,
Team Blog is a feature where multiple bloggers are able to contribute blog according to the assigned team.
Example, if you create a team called 'Team Z' in Team Blog, you assigned User A, User B and User C to this Team Z. When User A creates a blog post and set it to post under Team Blog(Team Z) as shown in the screenshot, the blog post will be able to view by User A, User B and User C only because the blog post is under Team Z and not public as usual.
Hope you understand my explanation.
You can check it out
here on how to set up a team blog.