A “flush” door describes a doorset where the door face sits in-line with the door frame. This differs to a more standard design where the door is set slightly back in the frame (or "recessed")
medium-density fiberboard
Flush doors have a simple, flat surface characterized by their sleek and minimalist look. These doors are made from materials such as wood, medium-density fiberboard (MDF), or veneer. They are particularly popular for spaces where a clean appearance is desired.