It's just hydrogen dioxide (H2O2) with some dish detergent and catalyst was added to speed up the decomposition of hydrogen dioxide into water... It's often called elephant toothpaste if you want to know more and do some research.
It's called elephant's thootpaste. H2O2 naturally breaks down in H20 (water) over time, you can speed up this process if you add a catalyst. And if the hydrogen peroxide releases a lot of oxygen at once in the presence of detergent, millions of little bubbles form quickly.
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