If you create a season, this is known as a "custom season" and the rest of the year would be known as the "default season."
For example, you could create a season called "summertime" that's from June 1 to August 31 and this might be your busiest time of the year. Now your default season would be January 1 to May 31 & September 1 to December 31.
Both your custom seasons & your default season will have unique pricing rules separate from each other.
It's important to note that pricing rules start to adjust from the present day. If the pricing rule is in a season setting, it will only apply if the present day is in that season.
Seasons are separate pricing rules, which means that time-based pricing rules won't adjust prices if there's a season there