All the Rage - S4-E3
Revealing mistake: In the very first shot, we see the sky, and you can tell it's a digital image imposed on a green screen instead of a shot of the actual sky.
Revealing mistake: When Jo comes riding in with the horses, you can tell that it's a stuntwoman in the far shot.
Chosen answer: It's basically just a type of suit that's made for whatever special project they're working on. No different than a lab coat, hazmat suit, fire coat, etc.