Universe is what we see, know and also what ever exists, what ever has existed, our past present and future. It include things we don’t know about, the world beyond milky way, different stars,anti matter,dark matter, multiverse universe and what not.
Our planet Earth is like a small bean present in one of the fruits in the an unknown branch of an unknown tree and that unknown tree is planted in dense unknown forest with variety of trees and perhaps different living organisms residing inside the beans of different trees.There are lots of beans inside a fruit, beans represent planets. The fruit is our Solar System, our branch is star (sun), we can observe nearby branches, their fruits, thanks to technology. So you can imagine how big is our universe. Scientists are saying there is a strong possibility of the existence of multiverse, which would also be included in the universe but that is an entire different subject.
So far we know three main things-
- Wave, particles- Particles are atoms, electrons, neutrons which interact together to form matter, elements, molecules. Particles form planets, sun, stars. Wave/particle is how these fused particles (stars) transfer their energy.
- Forces- Gravity, dark forces, electricity, magnetism etc. We know Sun’s pull (gravity) is responsible for keeping our planet rotating around the sun.
- Laws- We have defined laws like Newton’ laws, Mass energy equivalence equation, laws of gravitational forces to understand how these forces interact with particles (matter).