The document discusses complete denture impressions, which are negative registrations of the denture-bearing areas in the edentulous mouth. It describes the key anatomical landmarks and outlines the importance of complete denture impressions. The main types of impression techniques discussed are minimal-pressure, muco-compression, selective-pressure, and functional impressions. The document emphasizes the importance of border molding, tray selection and modification, and ensuring maximum tissue coverage and support while avoiding excessive pressure during impression-making.