To know what a hypothetical megastructure is you first need to know what a megastructure is. A megastructure is, well, exactly what it sounds like. It is a very large building. For example, the tallest building, the Burj Khalifa would be considered a megastructure. However, the definition of a megastructure is very loose. Megastructures are a rare appearance in the real world.
This is where hypothetical or sometimes called theoretical megastructures come in. They often appear in space, in pop culture books, films, and even video games. Theoretical megastructures are fictional. They appear in sci-fi, however are still based on facts and science. Most people probably know several instances of these without even realizing it. One example of this is ringworlds. They appear in the popular fps game, Halo. They are also seen in the novel Ringworld by Larry Niven, where it was first proposed, and the Disney Plus show, Boba Fett. Appearing in the ground breaking franchise Star Wars, the Death Star is one of the most well-known and iconic megastructures.
A dyson sphere is a enormous solar panel that encompases a star providing an extremely large amount of energy.
A dyson swarm is the same as a dyson sphere but it is made up of many smaller solar panels as pictured in the first image.
A ringworld is a large ring spinning at high speeds to create artificial gravity providing infrastructure is space.
A stellar engine, or shkadof thruster, uses the power of a dyson sphere or the suns to create thrust, pushing the star, and the solar system with it.
A skyhook is an very large tether attached to a wieght that would revolve above earths orbit. Incoming or outcoming spaceships would lach on to the end. The centrifical force of the tether would pfrovide and extra boost, cutting fuel consumption.
A stanford torus is very similar to a ringworld in the fact that rotates to create artificial gravity, but, the stanford torus is a torus, not a ring, and would be used as a space station instead of residential. The stanford torus appears in the award winning novel, Enders Game, writen by Orson Scott Card.
A O'Neill cylinder is in principle just a ringworld. It is a large cylinder using centrifical force to create artificial gravity. It would serve as orbital space colony. It appears in the sci-fi movie Intertellar, directed by Christofer Nolan, and is named Cooper Station.
A space elevator is and elevator that would reach out of Earth's atmosphere, providing easy acces to space.
I, Alexander Russ, am proposing a hypothetical megastructure of my own. I call it the Hawking Generator. It is similar to a dyson shpere but istead of harnessing the sloar energy of a star it would harness the hawking radiation of a black hole, hense the name.