Causation, or causality, is the capacity of one variable to influence another. The first variable may bring the second into existence or may cause the incidence of the second variable to fluctuate.
Causation is often confused with correlation, which indicates the extent to which two variables tend to increase or decrease in parallel. However, correlation by itself does not imply causation. There may be a third factor, for example, that is responsible for the fluctuations in both variables.
A statistically significant correlation has been reported, for example, between yellow cars and a lower incidence of accidents. That does not indicate that yellow cars are safer, but just that fewer yellow cars are involved in accidents. A third factor, such as the personality type of the purchaser, is more likely to be responsible.