From the introduction:
The Druid Spell Deck I contains all the Pathfinder RPG core druid class spells from level zero through level three in a thick poker card deck format.
This spell deck allows players to easily reference their class spells and even manage their spell slots with visual representation. These spell cards have the full spell text and mechanics within, so no need to hunt down the rules, you have them at your fingertips!
You can even use multiple decks to represent your entire number of slots and memorized spells!