Meaning of "non-normative"?

What's the meaning of "a non-normative document"?

Does "non-normative" mean "casual"?

What's the significant difference between a normative document and a non-normative one?

I typically see this in reference to standards and technical documents. A normative definition or statement is one that should be taken as authoritative or imperative (i.e., a should or a must), while a non-normative one is one that bears no such restriction.

Synonyms for normative would include prescriptive, so synonyms of non-normative could range from descriptive to declarative to informal or casual, depending on context.

Basically, it means "informal" or "nonstandard", as from the Free Online Dictionary:

Not based on a norm