Master pattern is a drawing showing the circuit traces, pads, holes for each layer of copper of each board. In the bad old days, circuit boards would be photo-etched directly from a master pattern of the traces made on mylar film.
Plan view is the view of the assembled/populated circuit board, as if you were looking straight down on it. Terminology comes from the building/civil types, where an elevation view shows the house as if you were to take a picture of it standing nearby, plan view is as if hovering above it in a balloon.