Destiny 2 · Armor customization
Armor mod slots
Each armor piece has four mod slots: one general slot for increasing a chosen stat and three slots for mods specific to that piece type.
How it works
The guide says armor mods can further improve a Guardian's capabilities. Of the four slots on each armor piece, one is for general use to increase a stat of choice, and three are specific to the piece type, such as helmet, arms, chest, legs, or class item. This passage does not enumerate individual mod effects.
Read the supporting references
Check the edition and source version for patch-specific details. Guide methodology.