In physical sciences, experiments can be conducted by isolating factors to see if what causes lead to what effects. For instance, if you put baking soda in a test tube full of vinegar, and it starts to bubble, you can be pretty sure that the baking soda caused the bubbling.
In politics, one cannot conduct an experiment in a test tube. The only way that one can make scientific study of politics is by examining it in daily life and comparing it with other situations. Through observation and comparison, one can hopefully learn enough about politics to make reliable predictions. That is the goal of comparative politics: observe two or more political situations, analyse their similarities and differences, and try to isolate causes and effects in order to make reliable predictions.
This wikiversity course will first start out by comparing basic theoretical concepts in politics. Then, it will compare political situations of different states with different political systems