i need help understanding

[twitch919]

hey guys. this might sound dumb but i don't understand scopes they confuse me i don't understand how you can zero in on them then switch to zero on a different range.how do you use the ?why is there's screws to tighten it don't you always have to keep changing it, how do you zero a scope? and bore sight it? im looking at a leupold mark 4 and it says" Once sighted in adjustment knobs can be zeroed" im having a hard time! whats the difference sighting in a scope and zeroing? how do i use the knobs right none of it makes sense i try to watch videos but they dont make sense !
also moa and the clicks on the scope

i pretty much need it in the most simpilest form :P
can someone help me!! sorry that it's so much to ask

THANKS

[one eye joe]

I will try to help. There are two knobs on the scope with markings which you adjust to get your rifle shooting where you aim it. They will be marked, usually up on one and right on the other to help in showing which way the adjustment moves the bullet. Once the rifles is hitting where you want, on many scopes you can loosen a screw or lift the adjusting knob and turn it so that the 0 on the dial can be lined up with a reference mark. This is called zeroing the scope. That way, you can check at a later date to be sure the adjustment knob hasn't been moved. Also, say your rifle hits 16' low at 400 yards from the zero you have set. Most scopes adjust 1/4" at 100 yards with each click of the adjustment, so you can move the up adjustment 16 clicks (at 400 yards each click =1"). You would then be able to aim directly at your target, make the shot, then move the dial back down 16 clicks which will line up your 0 again, and know that you are set for your original sight setting. Hope this helps a little.

[Ridge Runner]

yep sight it in, then loosen the setscrews, lift the knob turn it to zero, retighten the set screws. its sighted in and zeroed.
"0" just gives you a reference point, I sight my mark 4's in at 300 yards, then I can get to 1000 yards on less than 1 complete turn of the elevation knob (15 MOA).
each click of the scope moves it 1/4 MOA (minute of angle) until you get into really long distance you could call it 1/4 inch but it is slightly more.
RR