Plugins and widgets are the little apps you install on your blogsite to add functionality. They’re tiny engines that make interactive things work, handling almost any task: Search Engine Optimization, spam killing, email gathering, photo displaying… the list goes on seemingly forever. Choosing plugins and widgets can be among the most important decisions you can make about your WordPress site.
They’re created and supported by regular software developers who sell Pro versions of the free plugins found on WordPress. Still, the developers do like donations and they let you know on every page possible.