The relative pronoun "el que" (and its related forms) is used to refer to both people and things. Note that there are four forms to accomodate singular and plural, masculine and feminine: el que, la que, los que, las que. Mi tía, la que es profesora, viene a visitarme hoy día. My aunt, the one who is a professor, is coming to visit me today. Las mesas, las que son de plástico, son baratas. The tables, the ones that are made of plastic, are cheap. Mi tío, el que es taxista, llegará pronto. My uncle, the one who is a taxi driver, will arrive soon. Mis pantalones, los que son viejos, son muy cómodos. My pants, the ones that are old, are very comfortable. When the relative pronoun refers to an abstract idea, use "lo que." Lo que quieres no existe. That which you want does not exist. No comprendo lo que ocurre. I do not understand that which is happening. (On this sentences I personally would write "what" instead of "that which") http://www.studyspanish.com/lessons/relproelque.htm