Hello Taylor M.  In answer to your question, The Zohar is also called the, "Sepher ha-Zohar.  It's original spelling is in Hebrew.  It's title translates to something to the effect of, "Book of Splendor."  I consider the late Israel Regardie a reliable authority on this subject.  I'll quote its definition from his book, The Tree of Life, subtitled, "An Illustrated Study in Magic:"

"The "Book of Splendor," a huge Qabalistic text first published by Moses de Leon in the fourteenth century, but alleged to have been written by Simeon ben Yohai.  The Zohar includes commentaries on the Torah.  Moses de Leon is the probable author."

You may either click on the following link, or if that doesn't work, copy and paste it into your browser.  It's a link to Wikipedia's article on The Zohar.  As you may already know, Wikipedia is kind of like a community encyclopedia to which almost anyone can contribute.  As such, I find it somewhat prone to inaccuracy.  For some of the most authoritative information on it, consider the literature of any of the original members of The Golden Dawn.  For starters, here's the link:

http://en.wikipedia.org/wiki/The_Zohar