Biosignatures are indicators that suggest the presence of life, either past or present. These can be chemical compounds, physical structures, or patterns that are typically associated with living organisms. For example, the presence of certain gases like oxygen or methane in a planet's atmosphere can hint at biological processes. Scientists search for biosignatures in various environments, including on other planets and moons, such as Mars or Europa. By studying these signatures, researchers aim to understand the potential for life beyond Earth and to learn more about the conditions that support life in the universe.