It has the target turrets on the scope. Numbers on the turrets are 0-14 in both directions. The scope body itself has a line for both turrets to line the numbers up on this way you know what number you turret is on. When you get your rifle "zeroed" for what ever range your are shooting and say you have your turrets set at 7 clicks up for elevation and 4 right windage and thats your zero for 25 yards. Then while holding the turrets so they dont move you looses the turret screws then pull up or out on the respective turret and rotate it back to where the zero lines up with the line on the scope body. Now you are zeroed and the scope is set at zero's on the turrets.
This way if you have to add 5 clicks because of a breeze that day, your turret will be lined up with the 5 on the turret even with the line on the scope body. Then 2 days later you go out and no wind just set it back to zero and you are hitting your 25 yard "zero" again.
I have the zero locking turrets on my Gamo Hunter air rifle and my Romainian PSL rifle, copy of the Dragunov. I like them very much. Sounds complicated but once you get the hang of it its so easy. No more trying to remember how many clicks were added or in what direction.
Hope this helps.