Here’s the quick answer:
Widgets are sometimes included in plugins. They are not a type of plugin or separate extension for WordPress. Plugins can consist entirely of a widget, or add lots of functionality including a widget.
To further clarify, we need to cover exactly what widgets and widget areas are. Then the distinction between plugins and widgets will be quite clear.
What is a widget area?
A widget area is a part of a WordPress site where widgets can be added. The most common place for a widget area is a sidebar.
While you’re probably used to seeing widgets in sidebars, widgets can be added anywhere. For instance, the Apex theme has a sidebar that is the only “widget area”, and Apex Pro adds multiple new widget areas including an “After Post Content” widget area. Here you can see all the widget areas available in the Widgets menu:
And here you can see a widget displayed in the “After Post Content” widget area:
The availability of widget areas on your site depends on the theme. More widget areas provide more flexibility for displaying content on your site.
Now that you know how widget areas work, lets briefly cover exactly what widgets are.
What is a widget?
Widgets allow you to add content to widget areas on your site. They are always used to display content.
For instance, you’re likely familiar with the Text widget that lets you add text to a widget area, or the Recent Posts widget that displays a list of your most recent posts.
Plugins vs Widgets
Widgets are included in plugins for displaying content in a widget area.
Some plugins, like the Image Widget plugin, contain only a widget for displaying images. Other plugins, like the Meta Slider plugin, add new menus and settings while also including a widget for displaying sliders.
Plugins are the way we extend our WordPress sites, and widgets give us a way to display special content outside of posts and pages.