These give more information about the subject but not about what the subject is These relative clauses are not subject defining
I like to think of the commas surrounding a
non-defining relative clause.
Imagine that the whole clause can be removed.
The commas show us where the clause starts and ends.
Try removing the non-defining relative clause.
Does the sentence still make sense?
Practice removing non-defining clauses. Read this article. Find all the non-defining relative clauses, then read the text without those clauses. Did it still make sense?