An easy way to determine whether the fan airflow is up or down is to look a the fan blades as they rotate. The blades are installed on a slight angle. If the leading edge of the blade (the edge facing the direction of rotation) is up, the airflow will be down and when the leading edge is down, the airflow will be up.
During the winter, heated air rises toward the ceiling, and cool air settles toward the floor. Depending on the room size and shape, there could be a 15 degree difference between the floor and the ceiling. Naturally, people want the fan to pull warmer ceiling air down during the winter and vice versa during the summer.