Causal research investigates the effects of a variable on other factors. Scientists and market researchers often use causal research to verify the cause of a phenomenon or behavior. They also use it to predict the effects of actions.
For example, a cereal company might predict that changing the design of their product's box will increase sales. Researchers would show a wide variety of people the new box to make sure their prediction is right before putting the new box in stores.
Researchers have to be careful not to mistake a correlation for causation. A correlation means that two things are related, but one did not cause the other. For example, people who wear very large clothing have heart disease more often than average. However, large clothing does not cause heart disease. Both factors are caused by a third variable, being overweight.