Climate change is caused by many more factors than just two, so picking the two main categories is a bit difficult. If the scientific community could agree on two main categories of causes, there would likely be far less debate on the topic of climate change; however, I do think it is possible to provide two very broad categories.
Earth's temperature as a whole is determined by the balance between energy coming into the atmosphere and energy going out. If those energies are equal, Earth's temperature stays static. More energy out than in means the planet will cool, and more energy in than out means the planet will warm. All kinds of factors affect this balance, and those two factors can be divided into two huge categories. Some of the factors are natural, and some of the factors are human-made. A natural factor would be something like volcanic activity. A human-made factor would be our own carbon emissions or how we have changed the surface reflectivity of Earth with our buildings and roads.