Door: Sliding, swinging or folding panel on a closet.
Handle: also called profile or frame. Metal structure (in corrosion-treated steel or aluminium) which frames the panel and provides its aesthetic finish. It can be painted or coated to coordinate it with the panel.
Rails: guide a closet door or shelf. They can be equipped with brush seals and an anti-derailing system.
This is true for a sliding, folding or swinging closet door.