Armor and Speed is a feature in Rainbow Six Siege that determine the Operator's type. There are three different types: Light Armored, Medium Armored, and Heavy Armored.
Note: Rooks armor plates increase the armor rating of the Operator by one, i.e. Medium armored becomes Heavy armored and so forth.
Light Armored Operators take the full damage of a weapon but can traverse the map the fastest. Specializing in movement over defense, these Operators are better used in hit-and-run and roaming tactics.
Medium Armored Operators are the Jack-of-all-Trades of the three, as they take 90-85% of a weapon's full damage and traverse the map at a decent rate. Specializing in versatility above all else, these Operators are suited for the changing, dynamic tides of Siege.
Heavy Armored Operators are slow, but are the most heavily equipped, taking 80% of a weapon's full damage or 60% if using Rooks plates. More suited to holding down areas with their better durability, these Operators are best used for straight, one-on-one engagements.