JQuery is a JavaScript library that makes it easier to use JavaScript on websites. It allows developers to select HTML elements and perform actions on them with simple method calls. Some key points covered include how to include JQuery in an HTML page, common selectors to select elements, and examples of using JQuery to modify CSS styles and handle events like clicks and hovers. Events in JQuery allow responding to user actions, and methods like hide(), show(), toggle() allow changing the visibility of elements.