* Octagon: An octagon is a polygon with eight sides and eight angles. It has straight edges and sharp corners.

* Oval: An oval is a closed curve that is symmetrical about two perpendicular axes. It's like a stretched circle, with rounded edges.

* Planetary Orbits: While planetary orbits are not perfect circles, they are closer to an ellipse than an octagon. An ellipse is a special kind of oval.

In summary: Octagons have straight edges and are not curved, while ovals and planetary orbits are curved.