Non-defining relative clauses

1. We use non-defining relative clauses to give information that is not essential about someone or something. Non-defining relative clauses are always introduced by a relative pronoun ('who', 'which', 'whose' and 'whom')
1. My grandfather, who is 87, goes swimming every day
   
2. Yesterday I met a woman called Susan, whose husband works in London
2. Non-defining clauses give extra information to the sentence; if we remove the non-defining clause, the sentence still has the same meaning
1. My grandfather, who is 87, goes swimming every day / My grandfather goes swimming every day
2. Yesterday I met a woman called Susan, whose husband works in London / Yesterday I met a woman called Susan