The aberration of light is a phenomenon which makes the motion of celestial objects around their locations dependent on the velocity of the observer. Aberration makes objects to look like they are angled in the direction of the observer motion. The change in angle is calculated by the equaton v/c where v is velocity and c is the speed of light. Aberration is the difference in angle of the beam of light in different frames of reference.
With regards to the annual aberration of starlight, the direction of incoming starlight as seen in the Earth’s moving frame is tilted relative to the angle observed in the Sun’s frame. Due to the direction of motion of the Earth changing during its orbit, the direction of this tilting change during the course of the year and causes the apparent position of the star to differs from its true position as measured in the inertial frame of the Sun.