EL/LA/LOS/LAS QUE, EL/LA CUAL, LOS/LAS CUALES
The relative pronouns el/la/os/las que, el/la cual, los/las cuales are used in exchange for quien, quienes, hence when the sentence refers to people.En mi casa la que (quien) limpia es mi madre y el que (quien) cocina es mi padre.
In my house my mother is the one who cleans and my father is the one who cooks.
En esa foto están mis amigos a los que (a quienes) voy a visitar a fin de mes.
In that picture there are the friends to whom I'm going to visit at the end of the month.
We also use these pronouns when the sentence is introduced by a preposition but we can't use quien, quienes because the sentence refers to things and not people. When talking about things, the use of el/la/los/las que or el/la cual or los/las cuales is interchangeable.