Here’s a breakdown of each part:

1/ Styles: Styles are the vertical components of the door frame. They run along the entire height of the door and provide the structure and support for the door. Styles are often referred to as “vertical stiles.”

2/ Rails: Rails are the horizontal components of the door frame. They run across the width of the door and, like styles, provide structural support. Rails are often referred to as “horizontal rails.”

3/ Panel: The panel is the central part of the door, filling the space enclosed by the styles and rails. It’s often recessed or raised relative to the surrounding frame. The panel can be made of various materials, like  wood or glass.