system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What gives art its value?

Whats stopping me from painting a blue square and selling it for thousands? obviously i'd get zilch but proper artists can get away with it?
gpt
We give art its value. 

Its primary value is in what the art says. In 1917, an art museum was running a promotion in which they advertised that they would accept any form of art in their museum. Duchamp challenged this notion by submitting a urinal, signing it, and submitting it as a piece. The museum tried to protest against it, but Duchamp maintained that it was 'art', as there was no other criteria by which they defined art. 

It's now classified under 'Dadaism', which basically means that nonsense can be in itself an art form. Humans have a tendency to assign meaning to things even if they are nonsensical, which is what the art form draws on. 

The art in itself doesn't have to make sense, but we can pull meaning from it simply from the context in which it is being displayed. 

That's why people who go to museums try to stare at the art until they can figure out what it means to them; it draws on the context of the situation (i.e being displayed in a building specifically designed to display things of explicit and implicit meaning) to provide its value. 

'Conventional' art like paintings of people or places also carry meaning, but in a different way; it's about the presentation, perspective, or detail involved in a specific scene. 'Abstract' art bases its meaning on drawing your attention to things you might not have considered, which is why it's harder for most people to understand.