Originally Posted by AtomicDumpling
Fangraphs, Baseball Prospectus and Baseball-Reference are the best websites. Maybe toss Brooks Baseball in there too.
I would suggest reading Baseball Between the Numbers, which is a book published by Baseball Prospectus. There is also Extra Innings: More Baseball Between the Numbers. Another essential is The Book by Tom Tango and crew. The Numbers Game by Alan Schwarz is great for learning the history behind the traditional stats and why the new ones are better. Those are the best ones for getting a good, solid introduction to sabermetrics. Actually that is more than a solid introduction it is a solid education that is actually fun and interesting too.
Yep, hit most of them. I would say fangraphs probably has the best free resource on the internet for understanding the stats. They have tons of articles about the stats, and a library for all the stats that explains them. Just search the stat you want in their search bar. There will be a basic article on it and then the article will also link other web articles on the stat at the bottom. You will learn pretty much all you need to know about each stat.