A fact generally has more dimensions that define its minimum representation granularity, and it expresses a many-to-many relationship between these dimensions.
Typical dimensions for the sales fact are products, stores, and dates.
In this case, the basic information that can be represented is product sales in one store in one day, and it is not possible to distinguish between sales made by different employees or at different times of day.
Because facts are generally dynamic, a fact schema will almost certainly have at least one temporal dimension whose granularity can vary from the minute to the month (more probably, the day or week).
Dimensions are graphically represented as circles, connected to the fact by lines.