My jeep is making an odd clicking noise when it moves. What could that be and how much to fix it?

My jeep makes a clicking sound when I drive and only when it's moving. I want to know what it is and roughly how much it would cost to repair. Thanks.|||Is is making the sounds when you turn the wheel or switch gears?|||SOUNDS LIKE THE FRONT AXLE, EITHER THE DRIVERS SIDE OR PASSENGER SIDE.. I JUST HAD MINE DONE...