The given lines are y = 3x - 3 and y = 3x - 6.
To determine if the lines are parallel, perpendicular, or neither, we need to compare their slopes.
Both lines have the same slope of 3. Therefore, the slopes are equal.
Since the slopes are equal and not negative, reciprocal, or negative reciprocal of each other, the lines are parallel.
Therefore, the two lines y = 3x - 3 and y = 3x - 6 are parallel.