Every relative clause helps characterize a referent, but its dominant rhetorical purpose depends on whether the audience needs the description for identification or whether the description strengthens the effect of the predicate. Both purposes may coexist.
ExpressionChief contextual benefit
«الذي كان معنا أمس»Identifies a person whose name may be unknown
«التي هو في بيتها»Makes Joseph's challenging situation vivid
«الذي أحسن إلى الفقراء»May identify or prepare an expression of praise
The right classification requires context, the audience's knowledge, and the role of the subsequent predication—not simply spotting «الذي».