The ones on the right contain some exterior angles that are less than 180 degrees, giving them concavity. Not every exterior angle of these shapes is this way, but due to having some exterior angles like this, I called them concave. The ones on the left have none of these such angles.
The ones on the right contain some exterior angles that are less than 180 degrees, giving them concavity. Not every exterior angle of these shapes is this way, but due to having some exterior angles like this, I called them concave. The ones on the left have none of these such angles.
I agree with calling a straight a straight.