What is the difference between "roam" and "maneuver" commands?

When selecting certain units (tanks, for example) there's a "move orders" button at the very bottom of the commands bar on the right-hand side that pops out to choose "Maneuver," Roam," or "Hold Position." I can't tell what these do.

EDIT: I tried Move, Attack, Patrol, and Area Patrol with both Maneuver and Roam selected, and didn't see any difference.

"Maneuver" is equivalent to "Move" - your units will move to the target location.

"Roam" is like a patrol command except you specify an area instead of specific points to move through. When you click and drag with Roam, it'll show you the area the units will patrol. Roaming units will move randomly through the area. It's quite useful to have units roaming an entire planet you control if you want to stop enemy landings, for example.