K2-18b is a planet far away from Earth, so far that its light takes about 124 years to reach us. It sits at a distance from its star where water could be liquid, which is interesting for life.
Scientists using a powerful space telescope said they might have spotted a gas called DMS in the planet's air. On Earth, that gas is mostly made by tiny ocean creatures, so some people got very excited and wondered if it meant life.
But scientists are being careful. The signal was not strong enough to be sure, and when other teams looked at the same data, they did not all agree the gas was really there. Also, a gas made by life on Earth might be made in other ways on a different planet. So this is an exciting hint to study more, not proof of life.