There are several different camera views available in KSP, offering different perspectives from a virtual external camera pointed at the craft, kerbonaut, or other item being controlled. Pressing the V key will cycle through the available camera views at any time.
The free camera view positions the celestial body the craft is orbiting or resting on at the bottom of the screen and taking "up" to be a direction away from its surface. This is the recommended mode for controlling planes.
The orbital camera view takes "up" to be towards the north pole of the body being orbited, which tends to place the body to the side of the craft on the same horizontal plane when the craft is near the equator. This mode is often the most comfortable when flying a spacecraft in orbit as it matches the camera behavior of the map view.
While kerbals are in EVA on a planet, changing to Orbital perspective can cause the kerbals to flip on their sides, depending on the location on the planet. Gravity will still affect the kerbals, however.
The chase camera view is relative to the craft itself and rotates along with it as its attitude changes; it may also be repositioned manually. "Up" for the chase cam is based on the orientation of the part the craft is currently being controlled from (usually the command module). This view can make docking much easier to perform without switching to docking controls.
The auto camera view switches automatically between the free and orbital view depending on the craft's overall altitude. At launch the free view is used, but as soon as the periapsis gets high enough the camera switches to the orbital view (and back to the free view, when the periapsis gets too low). The minimum periapsis to switch to orbital view depends on the body: