Diffraction is a type of aberration in an optical system resulting from the constructive interference of light. In the JWST, the diffraction pattern is a result of the shape of the mirrors and the struts that support the secondary mirror. The mirrors were chosen to be hexagonal in order to create the largest possible reflective surface while minimizing empty space. Each of the 18 hexagonal segments are 1.32 meters in diameter, resulting in a 6.5 meter diameter total size. [2] The design was also chosen to be hexagonal because the primary mirror had to be folded in order to fit inside the rocket. As a result of these engineering constraints, the optical system of Webb creates these aberrations which we observe in the captured images. Note that these diffraction spikes are merely a result of the optical system -  they are not true features of the objects in which Webb captures.