Even though both jQuery and AJAX simplify browsing experience, and all are popular these days, their functions and operations are distinguished.

The simple difference is that JavaScript is a language while jQuery is a built-in library built for JavaScript. jQuery simplifies the use of JavaScript language.

One more difference is JavaScript is client-side, i.e., in the browser scripting language, whereas jQuery is a library (or framework) built with JavaScript. Meanwhile, AJAX is a method to immediately update parts of the UI without reloading the web pages.

Why do we use jQuery?

It is very easy to learn and use.

It is used to develop browser compatible web applications.

It improves the performance of an application.

It is very fast and extensible.

It provides cross-browser support.

Why jQuery?

There are lots of other JavaScript libraries out there, but jQuery is probably the most popular, and also the most extendable. Many of the biggest companies on the Web use jQuery, such as Google, Microsoft etc.

Summary

To summarise, jQuery is a fast, lightweight, feature-rich client-side which uses JavaScript library. Hope you picked up a thing or two.

Cheers!