Air defence refers to the measures and systems used to protect a country or area from aerial threats, such as enemy aircraft or missiles. It involves a combination of radar systems, interceptor aircraft, and surface-to-air missiles that work together to detect, track, and neutralize these threats before they can cause harm. Effective air defence is crucial for national security, as it helps safeguard military bases, critical infrastructure, and civilian populations. Countries often invest in advanced technologies and training to enhance their air defence capabilities, ensuring they can respond quickly to any potential aerial attack.