Magnetopause is that region where a magnetosphere is overpowered by the forces of the cosmos. The Magnetosphere is an electromagnetic barrier that surrounds many planets, though not all planets, and deflects the harder radiations that flow out from the planet's primary star, and the Universe in general.
The Magnetopause
A Google Source

The Bow Shock is a lot like the shock seen from the bow of a boat passing through placid waters. This is the point where two forces collide, such as the zenith at high noon (local time) on Earth, where the sun is most directly overhead. This is where the magnetopause interacts most forcefully against the incoming solar wind.
What is a bow shock?
A Google Source

Cheers,
Dan