"The lamp and the mirror hang on the wall."
Translation:Lampen og speilet henger på veggen.
"En vegg" is typically a wall of a building or a room, but can also refer to other types of walls providing privacy or shelter.
"En mur" is usually made out of bricks, stones or concrete, and often has defensive purposes. Think of the Great Wall of China, for example.
"-mur" is also used in compound words such as "grunnmur" (the foundation of a building), "brannmur" (firewall), and "bymur" (city walls).
It has been theorized that many European languages originally had noun classes such as animate, inanimate, and abstract. At the time sun, moon, men, and women might have been considered animate. While wind and water might have been considered inanimate. Then there was a third class conceived for abstract things like time, value, and weights. They subsequently became bastardized in creole languages, and conflated with ideas of masculine, feminine, and neuter. This is a gross simplification and some of my examples I've simply made up. But these individual fabrications are things that probably really happened in various European languages. They reflect a throwback to the idea, for instance that the sun and moon are alive, and are an indication of the culture and beliefs of ancient people.