Aberrations, or optical imperfections, exist because no lens is optically perfect. Almost all lenses show aberrations from the ‘perfect’ image.
Color fringing is another term for chromatic aberration, an effect where the lens produces color fringes around object edges. It's a very common lens aberration which is often corrected digitally. With some sensors and lenses you may also get color fringing around the edges of objects with very bring backlighting, such as leaves on trees against a very bright sky.