The eight volumes in this series contain a detailed list of the requirements for each grade of the Theory of Music exams, information needed in the context of the exam, specimen questions and exercises, and guidance on their solutions. Each book provides a sound foundation for anyone wishing to understand music theory as it is used in practice. A wide variety of music examples are used to illustrate the texts and to provide exercises. Revised Edition (2008).
I bought this one day at a library. If you are studying music theory, this is a good resource to start with. If you are confused, I recommend asking your teacher for a explanation.