A Dyson Sphere is a megastructure that has not yet been built. Scientists conceive of it as a giant shell that encloses the sun.
Hypothetically, the Dyson Sphere will be lined with mirrors and solar panels that will collect the energy from the sun. This would be an unimaginable amount of energy.
In theory, the Dyson Sphere would be large enough that it could be a habitable place for humans and it would act as an artificial biosphere in the case that Earth's supplies have dwindled. It would be a way to ensure survival for the human race.
In the Dyson Swarm, thousands of small mirrors or solar panels would orbit the sun like bees buzzing around a hive. The mirrors would then collect the sun's energy. The Dyson Swarm could theoretically be built using robots.
An article in Popular Mechanics explains how a Dyson Sphere could potentially bring back humans to life from the dead.
In the process, the Dyson Sphere will work in combination with artificial intelligence (AI). The highly advanced AI would collect historical and personal data about a human being so that it could make a digital copy of the human.
This copy of the human will be brought back to life biologically because the AI will use the human's DNA to build a clone. The human copy would live in a reality that is simulated. When it is time for the digital copy of the human to die again, they would be transported to a simulated afterlife. The process could then be repeated again so the human is reborn each time.
While this is not mainstream science and may be in the realm of weird science, there are a few scientists who are taking a serious look at the concept of immortality using a Dyson Sphere and artificial intelligence.