Not really A place, I learnt from Stack Overflow and various forums and examples around the web.
This might come in handy though:
Complete commands guide - http://api.jquery.com/
Similar but better presented - http://devdocs.io/jquery/
And this guy is pretty good explaining to beginners - http://thenewboston.org/list.php?cat=32 .. watch the first 3-4 videos. If you still find it complicated watch the first few videos of his JavaScript guide.