How do the listed MW4 aim controls work?

Editorial discussion starter from Modern Warfare 4 Cheats. This is a discussion prompt, not a customer report.

I am trying to understand the wording on the aim section. It lists an aim circle, smoothing, head or upper-chest selection, a distance cap, teammate skipping, downed-operator skipping, and a check for someone behind a wall. What does that actually mean in the listed controls? Review the current product page.