Quoting from my favorite Tarot site Aeclectic Tarot
The fool in colorful motley clothes, pack tied to a staff, a small dog, a cliff.
Basic Tarot Story
With all his worldly possessions in one small pack, the Fool travels he knows not where. So filled with visions and daydreams is he, that he doesn’t see the cliff he is likely to fall over. At his heel, a small dog harries him (or tries to warn him of a possible mis-step).
Basic Tarot Meaning
At #0, the Fool is the card of infinite possibilities. The bag on the staff indicates that he has all he need to do or be anything he wants, he has only to stop and unpack. He is on his way to a brand new beginning. But the card carries a little bark of warning as well. Stop daydreaming and fantasising and watch your step, lest you fall and end up looking the fool.