A Dyson sphere is a hypothetical megastructure that completely encompasses a star and captures a large percentage of its power output.
It would consist of a shell of solar collectors (or habitats) around the star. With this model, all (or at least a significant amount) of the energy would hit a receiving surface where it can be used.
The concept is a thought experiment that attempts to explain how a spacefaring civilization would meet its energy requirements once those requirements exceed what can be generated from the home planet’s resources alone. Only a tiny fraction of a star’s energy emissions reach the surface of any orbiting planet. Building structures encircling a star would enable a civilization to harvest far more energy.
Sort of like, Nidevellir in Marvel from where Thor gets his Mjolnir and Storm-breaker.
Or, on an even more advanced level, something like what was shown in Season 6 Episode 4 of Star Trek: The Next Generation.
Although such megastructures are theoretically possible, building a stable Dyson sphere system is currently beyond humanity’s engineering capacity. The number of craft required to obtain, transmit, and maintain a complete Dyson sphere exceeds present-day industrial capabilities.
Dyson Sphere is a theoretical possibility. It’s construction is now nothing but just an engineering problem.
Maybe in another 500,000 years, if we are still around, we might be capable of building such a structure. But there is always a possibility that that there are many civilization out there in the interstellar space who have already created such an extreme marvel of technology.
In Dyson’s original paper, he speculated that sufficiently advanced extraterrestrial civilizations would likely follow a similar power-consumption pattern to that of humans, and would eventually build their own sphere of collectors. Constructing such a system would make such a civilization a Type II Kardashev civilization.