I think hoochycoo is enunciating from within the 'restricted field of cultural production'. In this area 'Art' is different from 'art'. The differences are discursive - discourses that are enunciated both verbally (what people say/write) and in practices (what people do and where they do it: eg. prices of art works, how they are treated, where they are displayed, etc.).
The discursive differences that govern the difference between 'Art' and 'art' are quite subtle, and can be considered rules that people learn, wither osmotically, as they grow up in certain social groups, or intentionally, usually through attending tertiary education courses.
The rules have a certain class dimension, they can be mapped onto social class but not in an identical way - they diverge at significant juncture.
A lot of Art plays with these rules.
The idea that 'Art' has a semi-opaque language governing its status as Art tends to provoke a degree of hostility. I suspect that is because people, quite rightly, pick up on the exclusionary aspect of those rules.
However, it really is not hard to learn those rules, or to read about it.
That is a really, really simplified, unnuanced version of Bourdieu. And I hugely apologise for the lack of nuance.