Hi have you tried clicking onto Italki Resources at the top?

Hi Yilmaz, A relative pronoun relates the second part of the sentence ( after the comma) with the first part ( before the comma). Who : refers to the person mentioned in the sentence before the comma . This is the man . He owns a big factory . This is the man ,who owns a big factory ( Who refers here to the man , so instead of repeating ( man or he) we use "who" That/which : both refer to something mentioned in the first part of the sentence .It refers to objects and things but not persons . He is driving the car . It belongs to his friend . He is driving the car , that belongs to his friend. He is driving the car , which belongs to his friend. Whom : refers to a person too in the first part of the sentence ,but the difference between who and whom is that this person referred to in case of using "whom" is an object not a subject of the sentence She is talking with the man . She consults him about her business. She is talking with the man , whom she consults about her business. " The subject in the first sentence is "She" and the object is "the man",while "the man" in the other example ( this is the man, who owns the factory) is a "subject". I hope I clarified somehow the difference between who and whom ;)