
JQuery UI widgets and plugin are included in the same way in html page. They work like the same way as seems to me .Why their names are different ? What are differences between them ?
Please explain clearly.

Two main differences are given below :
1 Widgets are part of the jQuery UI library, where plugins aren't. Also, the Widgets have a visual component for the GUI, whereas plug-ins don't necessarily (although some have).
2 Plugins are functions that do something to your website. They could serve a back-end purpose and never be visible to you or the public. In the other hand, a widget usually is the representation of a plugin in the form of an object that can be placed somewhere on your website via the widgets interface under the appearance menu.
Note- Widgets are always plugins, but plugins dont always have widgets. A widget usually is a pretty and easy way of using a plugin.