GC-MS, or Gas Chromatography-Mass Spectrometry, is an analytical technique used to separate and identify compounds in a mixture. In the first step, gas chromatography separates the different components based on their volatility and interaction with a stationary phase. This allows for the individual compounds to be isolated for further analysis. In the second step, mass spectrometry identifies these separated compounds by measuring their mass-to-charge ratio. This combination of techniques makes GC-MS highly effective for analyzing complex samples, such as environmental pollutants, food products, and biological fluids, providing detailed information about their chemical composition.