One of the hardest things for Lisp newcomers to understand is symbols. They look tantalizingly like variables from other languages and, indeed, they are often just that. But, as the new Lisper soon discovers, they are much more.
Xah Lee just published a very helpful introduction to symbols in Emacs Lisp. His tutorial covers what symbols are and how they work in the context of Emacs Lisp. He also covers some of the functions that work with them and let you access the objects they contain. There is a companion page in which Lee shows you how to check if a symbol is bound to objects of various types.
If you're trying to learn Emacs Lisp, these pages will help clear up some of the things that I found most confusing when I started. These pages are a welcome addition to Lee's Emacs Lisp Tutorial series.