The main differences in between Interference and Diffraction are:
1. Interference occurs when 2 separate wave fronts originate from 2 coherent sources, whereas diffraction occurs when the secondary wavelets originate from different parts of the same wave front.
2. In Interference, the region of minimum intensity is perfectly dark, whereas in diffraction it is not perfectly dark.
3. In Interference, the width of the fringes is equal, whereas in diffraction it is never equal.