Brogue Wiki
You pass through the doorway.

A wooden door.

This is the standard door that you'll encounter throughout the dungeon. Creatures passing through a wooden door will automatically open it when the enter the door's square and close it again when they leave the door's square. Wooden doors are unusually flammable, they tend to burn down instantly.

Wooden doors are the most abused terrain type in Brogue. Whenever dealing with a monster that tries to maintain distance (pixies, centaurs, etc) step through a door and wait for it. It will periodically poke its head in, allowing you to bop it, and then it will run away.

Dropping an item on a door square will hold the door open.