The difference between a bug bomb and fumigation lies in their scale and effectiveness. A bug bomb, also known as a fogger, releases an aerosol insecticide to treat a confined space. It is typically used for surface-level pests like fleas or flies and has limited penetration into hidden areas. Fumigation, on the other hand, involves sealing a structure and introducing a gaseous pesticide that permeates every part of the building, effectively eliminating pests in inaccessible areas. Fumigation is more comprehensive but also more complex and expensive than using a bug bomb.