The Widget selector plugins define how multiple widgets of the same Entity Browser should be presented on the user interface.
For example, a site builder could create an Entity Browser containing 2 widgets: "Media Gallery" (a view) and "Create new media" (an entity form), and the mechanism to change between these two widgets is defined in the widget selector plugin configuration.
The Entity Browser base module defines the following widget selector plugins:
When configured to use the Single widget selection type, the Entity Browser will show only the first of the available widgets, and is naturally suitable for those situations where it makes sense to have only one widget available in the browsing experience.