You are looking at a command called build

build {location}
build {doorway} to {location}

Build makes new location as compared to a creating basic objects.

read the command called create to find out how to create basic objects.

Build has two ways of working:build {location} makes a new object called {location} in your current location with an 'exit' back out again.

build {doorway} to {location} makes a new {doorway} object (road,door,gate,path) that takes you to the new {location}.

Inside the {location} is a matching {doorway} returning you to your original location.

Some examples:
build a large kitchen
build a hallway to a large kitchen

read the command called location to change how players appear when viewing the location (eg you are on a cliff or behind a tree) instead of the default 'you are in ..'

You can paint your locations by standing in them and paint location

you can open the doorways and see them open on the other side. likewise lock paint and face effect both sides of the doorway.

All materials and associated material values (matavls) are inherited from your current location. So if you have made a room dark ( read th command called darken ), then build a corner in it.. the corner will also be dark.

Other location based materials are:
read the command called safehouse
read the command called setprivate

Other location base commands:
read the command called open
read the command called lock
read the command called paint
read the command called face
read the command called fortify

Doorways are two object linked together. you could manually create doorways like this:
create an aaa. type create a bbb
link aaa to bbb
get the aaa now go to a new location and drop the aaa and you have a doorway to and from your starting location.

(The build command does all of this hard work for you)
Code