I read that Cartesian Dualism is a subtype of Interactionism but I'm still confused. Can somebody help me to clear up this matter?
Through the famous Cartesian skepticism, Descartes concludes that the world is composed of two substances: res cogitans and res extensa. Res cogitans means thinking things, like consciousness, mind, or spirit. Res extensa means things that extend or occupy space. Material things in the world belong to the substance of res extensa. Descartes asserts that almost all things in the world are purely res extensia, governed by the causal law. To him, a dog is just a causal machine. A crying dog, then, is nothing but a whining gear. The only exception to him is human beings. To Descartes, human begins are made out of both thinking and extending substances. I, for instance, am composed of body (the materiel thing) and mind (the immaterial thing). This view of human beings can be called Cartesian dualism.
By positing that human beings are made of the two kinds of substance, Descartes ended up creating a problem. By definition, substance exists on its own right. So the thinking being and the extending being do not need each other, but they surely look like interacting with each other from my own experiences. My mind tells my body to exercise, but my body says it is too tired. I feel that I am just one whole person. If substance is defined by the way Descartes stipulates, how the interaction between them is possible? This question is called the mind-body problem, which has made the minds of philosophers busy even to the present time (under the topic of philosophy of mind).
Responding to your question, as Vimaior aptly put it, interactionism is a family of thinking (category) that aims to solve the mind-body problem. Viewed in this light, Cartesian dualism can be said as his own particular answer since Descartes solves the problem by positing that the two substances interact in the pineal gland. His solution is far from satisfactory since the question is not where, but how. Descartes' solution is contrasted by Malebranche's occasionalism and Leibnniz's pre-established harmony theory in history of philosophy. Malebranche argued that God is the one that enables the interaction in every occasion of causation between mind and body. Leibniz maintained God already knew that my mind wanted to scratch my nose at this moment so he arranged their interaction far ahead of time.