On card #1, you write something for the person on your right to draw.
Then everyone passes their stacks to the right.
You look at your newly-received stack, read card #1, then put it on the bottom of the stack.
Then you draw your interpretation of that writing on card #2.
Then everyone passes the stack to the right.
The person next to you looks at what you drew, then writes a description about it.
Man this is complicated, but basically you pass a stack of cards around in a circle and take turns writing descriptions, drawing that description, and writing a description of that drawing, and so on.
Here's one that I managed to scan and stitch together in Photoshop (a very powerful computer program used by professional artists worldwide).
That Photoshop comment wasn't supposed to be naive in a serious way.
Some of these things may never be posted, as they are too raunchy.