I learned some stuff about fermi paradox and alien worlds in past few days so I will try to do my best in describing this stuff. I found it really interesting.
So there is scale which is called Kardashev scale. It is scale that describes civilizations by three levels: Type I, Type II and Type III.
It is type that we are heading towards. Civilization of type I should be able to use all the available resources on its home planet which means it could fuse hydrogen into helium by nuclear fusion or it could use antimatter-matter anihilation to create enormous amounts of energy and would use sunlight, windpower or waterflow in large scales.
Type two civilisation would need even more energy which would cause in using all or almost all energy created by closest star (Sun). This “thing” is called Dyson´s sphere because it surrounds star and collects its energy. There are different types of Dyson´s sphere like: ring or swarm which are not that effective.
It is only extension to Type II because that civilisation would be able to use the energy of whole galaxy or multiple galaxies by Dyson´s spheres. Also there are some things like white holes or quasars which would also create a lot of energy so this type of civilisation could use them.
There is also extension for IV and V type.
4th would use whole universe while 5th would be able to use energy from multiple universes.