THE FOLLOWING IS STRICTLY FOR EDUCATION PURPOSES - NO LAWYER CLIENT RELATIONSHIP EXISTS UNTIL I ACKNOWLEDGE IT IN WRITING AND AM IN RECEIPT OF THE AGREED UPON RETAINER!
A cause of action is a legal theory under which recovery is sought. Some of the more common ones are negligence and breach of contract, fraud and replevin (I want my stuff back). Many have evolved over the last 1000 years from Judge made law, though some have been created by the legislatures. Below, I have posted a link to a guide I've used, the Wites & Kapetan Florida Litigation Guide which contains a much more detailed list. (I have no ownership or affiliation with Wites & Kapetan, I have simply used their guide myself in my litigation practice).
Basically, you can think of the legal system as a French restaurant, only serving certain things. If you want to eat there (or get legal relief), you have to order something on the menu. Causes of action are generally speaking, the only things for which the Courts will provide relief. So, whatever happened, it must be squeezed into one of the existing legal theories.
Each legal theory (cause of action) has certain elements that must be included in the complaint. If you fail to include one or more elements from a certain cause of action, you are likely to have your complaint dismissed and have to redraft it.
For a detailed list of causes of action and the elements required for each, see:
http://www.floridalitigationguide.com/contents.html on the Wites & Kapetan P.A. website (again, I have no affiliation with them, I'm just linking to their site).