Gaslaternen-freilichtmuseum Berlin is a place where you can see special lamps called gas lanterns. These were used in the past to light up the streets before electricity was invented.
In this museum, you can see lots of different gas lanterns from the olden times. They look different from the lights we have today because they use gas instead of electricity.
There are also many old-fashioned buildings in the museum that used to have gas lanterns outside. You can go inside these buildings and see how people used to live a long time ago.
It's a little like going through a time machine and visiting the past to see how things were done differently. It's really cool to see how technology has changed over time and to learn about how people used to light up their streets and homes.