it's mando'a, languadge of the mandalorians...
Reason it looks like storm trooper armor (or in this case slut trooper armor
) is because stormtroopers are second generation clone troopers, and the clones where cloned from, and taught by mandalorian Cuy 'val Dar, so it's no wonder the armor would be similar the beskar'gam worn by mando'ade.
The armor in that pict however was more likely than not modeled after storm troopers rather than mando beskar'gam but the principle is the same, you have an under suite that is normally a black form fit environmental suit fit for open space. You would then have a variety of plates that would snap onto the under suit. If you needed heavy armor for an open battle field you would use a heavy plate system, if you needed more maneuverability for a sniper you would use a light armor. That’s the beauty of the mando armor system.