Unit 2 Revision - Interference

In Young's slits experiment a pattern of dark and bright fringes are seen on the screen. Can you explain this in as much detail as possible?

a source of light is passed through a narrow slit which causes the light ray to diffract,
the diffracted light source now passes through a set of double slits - acting as coherent sources of waves - where the ray is diffracted again, these two sources of light have a constant phase difference and the same frequency.
the now two diffracted sources of light overlap and interfere, where they constructively interfere (arrive in phase) a bright fringe is seen and where they destructively interfere (arrive pi out of phase) they produce a dark fringe.
All the fringes on the screen are evenly spaced and parallel to the double slits