There are some 'terms' that will be used, that don't provide a lot of explanation as to what they really mean.  This page is meant to provide answers to those:

Stats, Bonuses, Penalties, Thresholds, Types, etc.

What do they all mean?

Let's begin with "Bonus"
A bonus is any identifier that has a "+" in front of a number, followed by a "%".
Example: Melee Weapons provides "+10%" Offense and "+10%" Damage.  These are bonuses.

Stats: These are not bonuses.  These are 'Base Scores' or 'Base Numbers.'  These are never given any sort of 'doubling' or 'tripling' or any other multiplier outside of the Number of Personnel still alive in the Unit.

Organic: A bonus is considered "Organic" if it's both A) a Bonus, and B) is written onto a character sheet.  Thus a Unit with Scout[3] has an Organic "+9%" to Scout checks.

Penalties: These are the inverse of bonuses.
Thresholds: These are the minimum results that must be rolled (1d100 + Total Skill Check [all applicable Stats and Bonuses]) in order to achieve some level of success.

Some items/effects/artifacts/whatever declare that "You cannot completely fail."

This reduces the "Threshold" for every success-type above (higher roll) than that mark, by its own amount.

Thus if an Artifact dictates that you can "Never Completely Fail a Scout Roll", this means 1-25 is no longer 'considered to be a complete failure.'  If looking at the Mechanics page: this would shift every block 'upward' by 25 points.  Meaning, if you roll a 1-25, it is now a partial success.  A significant success would occur on a 75, and an Astounding success would occur on a 125.

Actions: What is an action?  An action is a single, direction/location/target that a Unit, Group of Units, or Units + Leaders and Extras perform.

Thus, if you have ten Units, and you send them each to scout a different Grid; you have performed 10 Actions.  If they all band together for a turn to perform the same action (such as all scouting one Grid) that is a single action.

"Action Economy" is a meta-term you may hear spouted with regards to any game.  Action Economy is likely the truest form of 'meta' in nearly any game, and this one is no different.