In Chinese medicine, meridians are like roads in your body that carry energy called qi (pronounced "chee"). These roads are invisible and run all throughout your body, like maps. It's kind of like how roads on a map can connect different parts of a city.
When everything is working correctly, the energy flows smoothly along these meridians, kind of like cars driving smoothly down a well-paved road. However, if something gets in the way of the energy flow, like a blockage or an injury, it can cause problems, kind of like if there was a roadblock on a street.
Traditional Chinese medicine practitioners often use acupuncture, which involves inserting very thin needles into specific points along the meridians, to help restore the smooth flow of energy. It's kind of like removing the roadblock and letting traffic move freely again.
So meridians are kind of like invisible maps that show how energy flows through your body, and acupuncturists use them kind of like traffic cops to make sure everything is flowing smoothly.