Two-column themes are blog templates that feature a wide main column alongside a narrow sidebar. The main column typically displays blog posts, whereas the sidebar contains supplementary information and other blog elements, such as site navigation, banner ads and social buttons.
Blogs that are designed using two- or three-column themes are typically made to give enough exposure to blog posts and also bring more interactivity for readers through elements in the sidebar(s). In contrast, a blog with a one-column layout is devoid of sidebars so as to provide a distraction-free reading experience. Popular blogging platforms Wordpress and Blogger provide themes, both free and paid, in a variety of layouts.