In the introduction, Solomon is called "Koheles, son of David, king in Jerusalem." We can easily determine that this is Solomon. After all, he was the only son of David that ruled. (Also, David had no son or descendant named Koheles, king or otherwise.) So why was Solomon called Koheles? The name comes from the word meaning "to gather." He is called Koheles because he compiled many forms of wisdom, much of which is shared in this book. So, Koheles means that Solomon is "The Gatherer."
Much of the Book involves Solomon saying that certain activities are "hevel," normally translated as "vanity." For the purpose of our synopses, let us shake things up a bit. When you see us say that things are "temporal," "fleeting," "pointless," or words to that effect, you'll know that we're expressing the idea that Solomon referred to as "hevel," vanity.
Proceed to chapter one.