The section tag is used to define a section within a web page. Consider a situation where you had a book stored on a single page. You could use section tags to group chapters, or even sub-sections together.
The section is designed to be a logical grouping of data, but not necessarily be wholly self-contained like the article tag.
Each <section>
typically includes one or more heading elements and additional elements presenting related content.
I like to use the section tag to define a sidebar with elements in it such are recent posts, common links, etc. Each of those “sub-sections” contain data not necessary to the page, and they can have their own headers, etc. just as the specification recommends.
The Section Tag was originally found on Access 2 Learn