The Blog page is a usual blog, formed from the posts which belong to categories created by you, which have tags and featured images that show in the post listings on the blog page. You can set a page as a Blog posts archive page via Settings > Reading:
The blog page can have the sidebar on the left, right. or no sidebar, and the contents of the sidebar, as described above, are set under Appearance -> Widgets. Other settings of this archive page you can setup via Theme Options -> Archive pages:
Blogs can be posted by someone who has the access to the backend of the site with an admin or author role. Anyway, that person will be able to log into the WordPress panel and have a user profile.
The Default blog layout is a List layout and once you set up an empty page in the theme setting where it is said blog, it will show posts in the list layout.