So, maybe a stupid question, but...

... what precisely is infused armor and how does one get it?

I've seen it referred to a few times here, but nowhere else.

Infused armour takes less damage from a particular attack that the mursatt do. You get your armour infused in a mission at the copperhammer mines I believe.

Thank you much

The attack is Spectral Agony, from mursaats and jades.

The mission is Iron Mines of Moladune, but you can also get infused in Mineral Springs and the mission Ring of Fire.