Self propagating electro-magnetic waves. Otherwise known as light waves.
Electromagnetic Wave
Yes.
When a P-wave reaches the outer core, it undergoes refraction due to the change in density of the material. This causes the wave to slow down and bend as it travels through the outer core.
The general term for what a wave travels through is a medium, but in the case of earthquakes the wave travels through the ground.
The speed the wave is traveling through space
Light travels as light energy. Light is a type of electromagnetic wave.
the speed the wave travels threw space
There is no sound in space. Sound is a wave of energy passing through matter that we can hear, and in space, there is no matter for the sound to pass through, or at least the gasses that are there aren't close enough together.
The P-wave is a compression / longitudinal wave and so unlike the S-wave is able to travel through the liquid outer core.
A direct wave is a radio wave that travels directly through space without getting refracted by the ionosphere. In other words, it travels straight to the receiving antenna without being refracted.
reflection
Light travels as light energy. Light is a type of electromagnetic wave.