Earth’s axial tilt is approximately 23.44 degrees.
Also called obliquity, axial tilt is the angle between Earth’s rotational axis and the axis perpendicular to its orbital plane. More intuitively, Earth’s equatorial plane is tilted about 23.44 degrees relative to the plane of its orbit around the Sun.
That tilt, rather than changing distance from the Sun, is the main reason Earth has seasons. During Northern Hemisphere summer, the north is tilted toward the Sun, bringing higher solar angles and longer days. During northern winter, it tilts away, producing lower sunlight angles and shorter days.
The value is not perfectly fixed. Earth’s obliquity changes slowly over a cycle of roughly 41,000 years and is currently decreasing by about 46.8 arcseconds per century. The tilt is also distinct from orbital inclination, which describes the orientation of an orbit relative to another reference plane.