Elevation is how much up and down you can adjust reticle. For example, if you see in rifle scope specifications elevation is 3.5 m, this means that you can adjust reticle maximal 1.75 m up and maximal 1.75 m down for hits on your target at 100 m. Elevation range is usually specified in MRAD (1 mrad is 10 cm / 100 m) or MOA (1 MOA is 2.9 cm / 100 m). Some manufacturers designate MRADs with an acronym MIL.
Practically all newer rifle scopes have the possibility to adjust reticle left or right (windage) and up or down (elevation). This process is known as zeroing. Upper turret on rifle scope is for elevation adjustment of reticle and side turret on rifle scope is for windage adjustment of reticle. Hunter rifle scopes has the mechanism of both turrets protected with caps which protect turret from water, damage or any other outside impacts. Turrets are easily said a rotatable buttons which you can spin in left or right way.
Every single movement made with the turret produces a »click« sound. Usually 1 click on European rifle scopes moves hit on target for 1 cm at 100 m range (0.1 MRAD / MIL). On American, Japanese and Chinese scopes 1 click moves the hit on the target for ¼ MOA (minute of angle) which is 7 mm at 100 m range.
For long range shooting elevation of at least 2.6 m / 100 m (26 MRAD or 89 MOA) is needed.
Source: Revija Lovec