The WordPress.org Codex describes a WordPress Widget as:
WordPress Widgets (WPW) is like a plugin, but designed to provide a simple way to arrange the various elements of your sidebar content (known as “widgets”) without having to change any code. The Widgets SubPanel explains how to use the various Widgets that come delivered with WordPress, and the Widgets page at Automattic explains how to ‘widgetize’ themes and plugins.
Great How to Build a Widget Tutorial from LonewolfDesigns
How to make a WordPress Widget from Scratch
Resources



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