Relative to the car you are motionless. Relative to the road you are moving at the speed of the car. Relative to the sun you are moving at the speed of Earth as it orbits the sun (30km a second).
Relative to the car, you are at rest. Relative to the road, you are moving if the car is in motion. Relative to the sun, you are moving with the Earth's rotation and orbit around the sun.
From your perspective inside the car, you are at rest relative to the car. You are moving forward relative to the road outside. Your motion with respect to the sun is a combination of the car's motion and the Earth's rotation, so you are also moving along with the rotation of the Earth.
the point of view that you describe motion from is whatever you choose it to be. generally we describe motion relative to earth. for example you could say that a car is moving 60mph north, and it would be assumed to be moving relative to earth; but if someone is riding their bike 10mph north, then the car is moving 50mph north relative to the bike. you see, you could describe the car moving compared to a star in a distant galaxy if you wanted, but that would be useless information so you should choose something relative to the problem.
The bike. Even though you and the bike are in motion the positions do not change.
You are not moving relative to the bicycle.
riding a horse ;)
An example of relative motion is when you are riding in a car and another car passes you on the highway. From your perspective, it looks like the other car is moving quickly past you, but from the perspective of someone in the other car, it appears that you are the one moving backwards.
showjumping/
A heavier car has more inertia, resistance to a change in motion, than a lighter vehicle. Therefore in the event of a crash the lighter vehicle will have a greater change in motion relative to the heavier vehicle; the less the change in motion, the safer.
Building.
You are not moving, if you are comparing to the car.
Here's one example. Suppose you're on a train. Now let's further suppose this is a very smooth-riding train and that the windows are covered up and you've never been on a train before. As long as the train is going straight (no curves, no hills) and not accelerating or decelerating, it would be very difficult for you to tell you're moving relative to the outside world: everything in the train is moving at the same speed you are, or, to put it another way, you're all in the same frame of reference. That frame of reference may be moving 60 miles per hour relative to the outside world, but everything you can see or measure appears to be standing still.