Hierarchy is used in design to highlight the important elements first. Jo sbse jada impotant wo sbse highlighted and usse kam wala kam highlighted.
Alignment is used to prevent design from being disorderly mess. Similar object (group) ko similar align krni hoti hai (Left, centre or right me se)
Proximity is grouping similar object together. Like all the visual element/illustration/pngs ko sath me rakho and text/bullet points/buttons to sath group krna hota h .