In WordPress, a sidebar is a widget-ready area for use in WordPress themes to show content that is not part of the primary content for the page. It does not always have to be a vertical column to the side. It can be anywhere the theme allows: a horizontal rectangle above or below the content area, header, footer, and more.
The choices of the WordPress developer dictate the usage of the sidebar, and this usage varies. Several WordPress themes support numerous sidebars, also referred to as widget-ready areas.
When designing the blueprint of your WordPress website, sidebars are very important for displaying content that is not part of the main content of the website. Examples of information that can easily be displayed across the site with the use of sidebars includes recent comments, a list of some recent content, your full menu of pages, popular articles, etc. Sidebars also provide the room to place advertisements on the page from the occasional third-party website.
If users wish to drag and drop some new items into their sidebars, they can do so by going to Appearance, then Widgets within their admin panel. There are a number of WordPress themes that come with especially configurable options, such as allowing users to drag and drop their own sidebars into different areas of a website. This provides a way to generate dynamic layouts.