In Photography Life, Nasim Mansurov explains that chromatic aberration is caused by the inability of a lens to focus incoming light to a common focal plane, and /or color wavelengths focusing at different focal plane points. Because of its effect on photographs, chromatic aberration is also sometimes called "color fringing" or "purple fringing."
Mansurov expounds on this explanation by saying that chromatic aberration is caused by lights of differing colors passing through a lens at different speeds, technically termed lens dispersion. The resulting photograph can show colored edges around objects, particularly in high-contrast environments, or a simple blurring of the entire image. A circle of least confusion, the location of the best focus in which a lens focuses all wavelengths to a single focal point, would occur with a perfect lens.
Mansurov goes on to explain that one type of this phenomenon, known as longitudinal chromatic aberration, occurs when different wavelengths of color do not meet at the same point after passing through a lens. The other type is known as lateral chromatic aberration or transverse chromatic aberration. This occurs when color of differing wavelengths enters the lens from an angle and focuses along the same focal plane but at different positions.