In situ resource utilization

In situ resource utilization (ISRU) is when we use the resources found on a planet, like the moon or Mars, to make things we need. For example, if astronauts are on the moon or Mars, they can use the resources found there, like the rocks, soil, and ice, to create the things they need. This way, they don't have to bring all the supplies they need with them - they can just make them on the planet using what is already there.