How does a portable power station work?

At present, these oversized batteries are lithium ion technology. They do not generate electricity. You only need to charge them from ordinary wall sockets, car cigarette lighters or separately sold portable solar panels, and they will store electricity until you need it.
Compared with gas generators, battery-powered power stations have two main advantages: you can store them indoors or use them in cars, and they are silent. But they are more limited than gas generators: they will not operate refrigerators, nor are they really designed to operate high-load equipment, such as space heaters or even hair dryers. But a good laptop can easily charge the laptop several times, or run the CPAP machine all night, or power the small lamp or fan.