A General Overview and Why Would I Need It.

A General Overview and Why Would I Need It.

Greetings,
 
I browsed the other postings first, and didn't find what I wanted. Please forgive if I overlooked the information and repeat the question. Please point me in the right direction.
 
I stumbled upon jQuery.com mentioned in a podcast, and thought I'd take a peek. I've been programming for many years and jQuery has crossed my path many times. It was one of those things I kept putting on the back burner until I could give full attention to it. And, well, you probably know the rest of the story. Nevertheless, here I am. I thought this might be a FAQ, but I didn't see it. I want to begin with the right expectations/understanding.
 
Question:  Where can I find a high-level overview of jQuery, what can it do for me, why should I learn it, what do I need to know going in? etc.
 
Thanks in advance,
Randy