Usually WordPress themes have one or two different sidebars. They are located on the left or right side of the content as this depends on the theme settings. Some themes also support footer sidebars.
Each separate section in the sidebars is a widget and it contains certain information. The widgets are accessible from the Appearance -> Widgets menu.
All available widgets are listed in the Available Widgets section.
To activate a widget, you need to click, drag and drop it in the respective Sidebar on the right.
Then you can set a widget name which will be displayed as a section title. If necessary, you can change further settings of the widget. After you click on the Save button, the widget will be displayed on your website.
To disable a widget, click, drag and drop it in the Inactive Widgets section at the bottom of the page.
The Delete button does not automatically move the widget to the Inactive widgets, but only removes it from the sidebar.
To work with the widgets in a preview mode without the changes shown live on the website, click on the Manage in Customizer button. The Customizer is used for design and development of the appearance of your website, theme, menus, widgets, etc. When you make changes on that page, they are not applied to the website. To apply them on your website, click on the Save & Publish button.