MIL
MIL is short for MilliRADian, which is another angular measurement. It is much the same as the description for MOA, but with different values. At 100 yards, that flashlight beam of 1 MIL projects out to 3.6 inches. At 1000 yards, it becomes 36 inches. The military uses MILS because they simplify range estimation and provide precise angular measurements for targeting, which are crucial for artillery, fire control, and navigation. Since 1 MIL corresponds to 1 meter at 1 kilometer (or approximately 3.6 inches at 100 yards), soldiers can quickly and easily estimate distances to targets and calculate the necessary corrections for accurate fire. Simple.
On a MIL scope, each "click" is typically 1/10th of 1 MIL. At 100 yards, a single click will adjust your point of impact by 0.36 inches. At 1000 yards, a single click will adjust your point of impact by 3.6 inches.
The good news again? Don't sweat all this jargon. Learn it, know it, but don't sweat it.
Why? Because the RETICLE inside any scope is also broken up into smaller subtensions so with proper training using your reticle, you can very closely approximate how many "clicks" are needed in order to shift your point of impact.
Much more on scopes and reticles later. Try and digest this all first. But believe me, it DOES NOT MATTER what type of scope you have, you will just learn to use it. The ONLY caveat on this is to say that if you have a shooting partner, it is handy to use the same type of scope as him or her. If you use them as a spotter while you shoot and you spot them when they shoot, you want to be talking the same language. If both are on MIL, you talk in MIL. If one has MIL and the other MOA, one of you will be trying to convert numbers.