Ready Event in jQuery is to prevent any jQuery code from running before the document is finished loading (is ready).

It is good practice to wait for the document to be fully loaded and ready, before working with it.
This also allows you to have your JavaScript code before the body of your document, in the head section.

The handler passed to .ready() is guaranteed to be executed after the DOM is ready, so this is usually the best place to attach all other event handlers and run other jQuery code.