A vision is a picture in your mind and heart and even soul of where you want to go. It drives you relentlessly towards a certain destination.
The difference between not having a vision and having one, is the difference between taking a Sunday afternoon joy ride or going on a one way road trip.
The first is easier, fun, and usually filled with lightheartedness. Each trip you say, "I hope everyone enjoyed their time, maybe we'll do it again next Sunday." After the trip you end up at the same place you started, just out of gas.
The second can be at times arduous and tiring. Each stop you say, "It's a mighty long journey, but we're on our way." It is filled with adventure and accomplishment, and in the end you find yourself in exciting new territory.