HOW TO PLAY SET
The deck consists of 81 cards varying in four features: number (one, two, or three); symbol (diamond, squiggle, or oval); shading (solid, striped, or open); and color (red, green, or purple). Each possible combination of features (e.g., a card with three striped green ovals) appears precisely once in the deck.

A set consists of three cards which satisfy all of these conditions:

They all have the same number, or they have three different numbers.
They all have the same symbol, or they have three different symbols.
They all have the same shading, or they have three different shadings.
They all have the same color, or they have three different colors.

Given any two cards from the deck, there will be one and only one other card that forms a set with them. One example of a set would be these three cards:

One red striped diamond
Two red solid diamonds
Three red open diamonds