The answer to 'difference between flashing' is that flashing is a critical component of a roof system, used to prevent water intrusion at points where the roof meets other building elements. There are two main types of flashing: roof-to-wall flashing and step flashing.
Roof-to-wall flashing is used where the roof meets a vertical wall, and it helps direct water away from the wall and onto the roof. Step flashing is used for roof sections that intersect, such as where a dormer or chimney meets the main roof. Step flashing overlaps the shingles to create a water-resistant barrier. Both types of flashing are important for maintaining a watertight roof and preventing costly water damage.