Gas chromatography is a separation technique that uses the differences in how compounds partition between a mobile gas phase and a stationary liquid phase. It works by injecting a sample mixture into a column, where each component interacts differently with the stationary phase and moves through the column at different rates, allowing separation. Key components are the carrier gas, injection port, column, oven, and detector. Factors like temperature, carrier gas flow rate, and column length affect separation by impacting how long each component is retained in the column.