“jQuery UI is a widget and interaction library built on top of the jQuery and JavaScript Libraries, that we can use to build highly interactive web applications. ”

"Widget" to me means a user-interface element, like a button or something more complicated like a popup date picker, but in jQuery UI terms it means a class, members of which are associated with HTML elements; things like Draggable and Sortable
The jQuery UI project was originally created to bring us a set of "official" jQuery plugins. Mature components from the plugins repository were pulled together to form the first release of jQuery UI. But since each of these plugins had its own style, having been written by different authors.
We can Download jQuery UI library from http://jqueryui.com/download website to download a copy of jQuery UI. jQuery UI's download builder allows us to choose the components we would like to download and get a custom version of the library for your project. There are 3 easy steps to building our custom jQuery UI download:

Step 1: we can choose the components what we need

Step 2: we can select a theme or we can custom our own theme

Step 3: we need to Choose a version of jQuery UI

So finally we have downloaded the Jquery UI interaction library.

we will see how to work on jquery UI in my next post.