You have already heard about javascript but jquery is little confusing to new coders. The matter of fact is that with the advent of new programming languages it is becoming easier of programmers to code and overcome their needs. Now programmers want that they write less code and have more functionality in the code. With less code in mind, jquery was thought to be created. But first I want to tell you what the heck jquery is. Jquery is also javascript but it is javascript library. That mean some methods are defined in this library that do certain tasks like you want to animate anything then certain method you have to use instead of writing the code from the start.
If you have heard about ajax then doing ajax in jquery is very easy. There are many methods in jquery that can do ajax with very little code and is also very easy to undertand the code. Ajax is that data is retrieved or send to other pages while staying on the same page or you can say without page refresh. Now there are many jquery plugins are available which use jquery code at the backend and gives their own task of functionality in it.
You may have heard about different frameworks like codeigniter is php framework which hide many complexity of php code and work in style of writing less code and having more functionality. So jquery is also like a framework which does more and we have to write less code. Javascript is a complex scripting language and doing some tasks become very difficult in it. I had been working on project and was using javascript and the way I want to do something was looking impossible in javascript, so I downloaded jquery library, read some documentation from jquery official website and do some research and finally my work was done and my client also become happy. So hope you also try jquery yourself and you have more fun using it.