Why/how do planets revolve around the Sun in orbits?

The solar system formed out of a disc of gases. As the planets coalesced they started to take on all the matter that was in their path by running into it. They continued to grow until they had cleared everything out of their path except for themselves. That's why they rotate around the sun in their own unique orbits. The motion was already there before the planets came together.

All the planets in out solar system are roughly on the same plane. That is congruent with the hypothesis that they formed out of a disc of matter. If you look at some of the moons in our system they are in retrograde orbits travels the opposite direction around their host planets. these moons were captured by the gravity of their host planet. anytime an object moves in a weird way like that the most likely culprit is that body was captured by the gravity of another body.

inertia the fact that objects continue to move in a straight line unless pushed or pulled (acted on by a force

the force is gravity

the is something that is called "conservation of angular momentum" that takes more understanding

it is possible for an object to come past the sun and then leave never to return, it has to be moving fast

look up "escape velocity"