What is Particles and entity variables

so first i was making a unit touching a another unit but first i saw this Entity variables
so i wonder what that is but i cannot add it or anything but a few days ago I saw particles and i wonder what it is too Maybe something cool? maybe it will make me smart? who knows…

Particles we can say, they are “Projectiles”, only to effect, like, walking creates a Projectile, we call it a particle, I don’t know if and this, but this is a theory of mine, why there are nothing about, and as there are in the units in the effects, InMove, there is one that is create a projectile, so I think this is a particle, a Projectile to decorate.
Well, I know what entity variables are, say and a “private” variable, the one that only has one unit (a player), like a boolean in the entity variable, only in humans, not in the NPC, this will only happen in unit (player that controls the unit (because it is private)).