Is there a difference between framing in a room not being "square" and studs not being "level"? And how would each impact the hanging of drywall and the appearance of the completed walls if left uncorrected?

Urgently needed information- please respond asap.

Thanks.

Level refers to the vertical position of the studs and how plumb they are, a level stud would have no vertical angle on it if you held a level up to it. Level could also refer the top and bottom plate, which horizontally should be level. Square refers to the corners, a square corner would be 90 degrees. How it would affect the drywall if they were not square and level depends on the extent they are off. It would hard to notice a wall that is just slightly off level and square.

amricca is correct. It also depends on what you are doing with the walls.

square corners are more important if you are installing cabinets or tubs or shower enclosures (although there is always room for some play). So for example, if you are doing a bathroom, ensure the walls around the tub are square. Moulding will also be more finicky to install if corners aren't square.

vertical walls are more important if you are installing tall furniture like a wardrobe, fridge, or display cabinet of some kind... although it would be unusual for new construction to be out far enough that is is really noticeable.

What is most noticeable are walls that are 'wavy' (i.e. studs don't line up, so the drywall curves in and out between studs.) You may want to check walls with a straight edge (i.e. a straight 2 x 4) placed horizontally across the wall before you attach drywall.

Would walls being "out of square" mean that the walls would be wavy?

Or would the studs not being "level" result in the walls being wavy?

The studs not being in alignment horizontally would make the wall wavy, they could still be square and level.

We need Harold with one of his excellent drawings!

The most common reason is that the studs are bowed. Imagine looking straight down a hallway and seeing the wall with bumps and hollows on it - that is what you are trying to avoid.