Obliquity refers to the tilt of an object's axis relative to its orbital plane. For example, the Earth has an axial tilt of about 23.5 degrees, which affects seasonal changes. This tilt causes different parts of the planet to receive varying amounts of sunlight throughout the year, influencing climate and weather patterns. In astronomy, obliquity can also apply to other celestial bodies, such as Mars and Venus, each having its own unique axial tilt. Understanding obliquity is essential for studying planetary climates and the potential for habitability in other parts of the solar system.