Near-Earth Objects (NEOs) are celestial bodies, such as asteroids and comets, that come within 1.3 astronomical units of the Earth. They are classified into two main groups: Near-Earth Asteroids (NEAs) and Near-Earth Comets (NECs). NEOs can vary in size, from small rocks to larger bodies several kilometers wide. Scientists monitor NEOs to assess any potential threat they may pose to Earth. Tracking these objects helps in understanding their orbits and predicting their future paths. Programs like NASA's Planetary Defense Coordination Office work to identify and characterize NEOs to ensure planetary safety.