In 2D, the design plane is parallel to the screen and, in effect, you view the model from above. The default (unrotated view) in 2D is like a Top view with its orientation such that:

• The x-axis is positive from left to right (horizontally).
• The y-axis is vertical, and positive from bottom to top (vertically).

In a 2D model, you rotate a view about an imaginary z-axis, which is perpendicular to the screen. No matter how you rotate a view in 2D, effectively, you still view it from above.