The panel is the actual door. A door panel and the surrounding frame create the entrance to a space. The door typically swings open and closed on hinges.
The hinges allow the door to swing open and closed. The door's hinges are attached to the hinges on the door frame by hinge pins. Remove the pins to remove the door from the frame.
Some door panels are solid. Others have windows, sometimes called "lights" or "glazings," that allow light in and allow people to see through the door. Muntins are the wood pieces that hold glass windows in place on a door panel. Stiles are vertical pieces of the door panel that are on the left and right of the window glass, while rails are two horizontal pieces of the door panel above and below the glass.
Some solid entrance doors have keyholes, small holes through which a person can look from the inside to see who is on the other side. Keyholes are typically one-way sight lines only.
The latch set is the door's latch and handle or knob. It holds the door shut. It is typically mounted about 36 inches off the floor and attached to the door panel and frame. The part on the door panel lines up with the part on the frame when the door is closed. The handle or knob piece is always attached to the door panel.
The lock set is the deadbolt lock device commonly found in building entry ways and the exterior doors of home, condos or apartments. It keeps the door shut and locked, and can only be unlocked from the inside or with a key from the outside. Like the latch set, the lock set has pieces that attach to the door panel and to the frame, which can interconnect when the door is closed.