The center content of our WordPress blog site will display posts or page content as set up for that page. It could show all posts in a category, or static content if we've designed a page that way. What the sidebars do is display specialized content on every page of our site. The center may change, but the sidebars will stay the same.
There are more advanced techniques and widgets that may make a sidebar different on the home page than on others, but we'll stick to sidebars that display the same across the site for now.