Core card sets feature a number of different shaped cards that are placed at the center of spread.  You can use a core card with any tarot, oracle, or prompt deck you like. 
 
To use the cards: Simply place prompt/oracle cards around the edges of the core. The labels on the core tell you what each card represents. More tips and directions for use are on the back of each core card. 
 
CARD DETAILS:
32 cards for Intuition and Inspiration spreads
Printed on thicker 16 point stock in full color. 
Smaller squares/diamonds are for 4 card pulls.
Larger squares/diamonds are for 7 to 8 card pulls.
Thinner rectangles are for 8 card pulls.  
Hexs are for 6 card pulls.