Максим Ачкасов - Ограничительные определительные придаточные предложения в английском языке

We use defining relative clause to identify a thing or a person what is being talked about. To refer to people that and who can be used. To refer to things that and which can be used. If we speak about superlatives or the words like something, someone, anyone, everything, we should use that only. Commas aren’t used to in defining clauses.