Knowledge from God
Where there is no vision, the people perish: but he that keepeth the law, happy is he.
"Vision" is revelation or knowledge from God.
When God's Word directs your path you walk rightly. You are happy and prosperous and go straight forward without wandering. Where there is no knowledge of God, people have no guide or protection. They are like a dog loosened from the direction of its master. They wander aimlessly.