Power Memorization
Certain classes will grant Memorized Powers in addition to your Mastered Powers. While your Mastered Powers don't change, your Memorized Powers serve as variable power slots that can be changed out after every Extended Rest. Think of them sort of like a wild card, where you determine the value of the card at the start of each day.
Each Power Memorization is limited to a specific Caliber (i.e. Basic, Advanced, Legendary, or Ultimate), though you may always choose to memorize a power of lower caliber in place of a power of higher caliber. You may only memorize powers for which you meet the prerequisites.
At the end of each Extended Rest, your character spends time preparing their Memorized Powers for the next day. The specific amount of time and method for completing this process is determined by your Class. Your Class may also put restrictions on which powers you can memorize (i.e. Wizards must have a copy of the Spell in their Spellbook and Clerics must choose from their selected Disciplines). Certain Specialties, Talents, Magic Items, etc. grant you additional Power Memorizations and/or allow you to use your Memorized Powers in enhanced ways (i.e. Swapping Memorizations during a Short Rest, using Mastered Augments in a limited capacity, etc).
When utilizing a Memorized Power, you may use Augments, but not Master Augments. Though you have added versatility with your Memorized Powers, they are not typically as powerful as your Mastered Powers.