Student or Learner
I'm reading and studying a grammar book.
During that, I met a difficult sentence and haven't understood its structure and meaning.
The sencence is like following.
The framework of analysis is one in which form, meaning, and use are seen as interconnected aspects of what it is language users know when they know a grammatical construction.
Especially, I don't understand what that 'it' is.
I managed to understand the sentence before 'what',
but I don't understand the part 'aspects of what it is language users know'.
Anybody please help me understand the structure and meaning.
I don't wanna bother you but could you please rewrite the sentence in a easier and plainer structure?
Thank you very much.