Can someone explain to me how this can be good for your body

It's called cupping. Here are some potential benefits:

Brings the blood to specific spots/muscles on the body. Blood is where ur white blood cells are. Thats how you heal.

Cupping therapy is an ancient technique where cups are used to suction the skin, believed to start in China around 3000 BCE. It's been used in many cultures and still popular for its supposed benefits.

It’s actually feels good sometimes the process involves puncturing a small hole with a needle so the blood will be sucked out too

Benefits: Fire cupping is believed to increase blood flow, which may reduce pain and promote healing  It may also break up lactic acid in muscles Side effects: Fire cupping may cause bruising, burns, mild discomfort, and in rare cases, mild infections

Here you go, buddy:

Turning your back into pepperoni 🍕 😂

Fire cupping therapy

It lets all the air pressure out your back