DOPE
This is an acronym for "Data On Previous Engagement" and refers to recorded information from past shooting experience which can take the form of a "Ballistics Table", a "DOPE Card", or from a "Ballistics Calculator". After acquiring the BC of the bullet you shoot and the VELOCITY of that bullet, you can begin to develop the "DOPE" on how your rifle shoots using that ammo. You will find that your particular ammo will drop a certain amount at varying distances which allows you to compensate for the drop by adjusting the ELEVATION turret on your scope.
As an extreme example, let's say that I have the BC and Velocity for my bullet, I plug it into a Ballistics Calculator (more on that later), and it tells me that my bullet will drop 30 FEET over 1000 yards. You read that right. If you just took your rifle out, which you know you can hit the bullseye at 100 yards and aimed it at a 1000-yard target, you will fall short and fall short HUGE. Think of it this way, you would have to aim 30 FEET above the 1000-yard target to have any chance at hitting it. Try and measure 30 FEET up looking at a target that is MORE THAN a HALF MILE away.
What you CAN do, is dial your scope according to what the ballistics calculator says, put the crosshairs on the target and shoot.
Placing the crosshairs on your target after the scope adjustment will cause you to elevate your barrel to compensate for that 30 foot drop your projectile will experience in flight.
How can I know how much to adjust my scope elevation to consistently hit a target at distance?
A DOPE card is essential to consistency.