Relative pronouns que (that) and quien,quienes (who) are used to combine two sentences with a common noun or pronoun into one sentence.

​Is the most commonly used relative pronoun. It can refer to people or things.
Unlike that in English, que is never omitted.

Que

Refers only to people and is used after a personal a or preposition a, con, de, para, por, en.
Quien(es) may replace que when the dependent clause is set off by commas.

​​Quien, Quienes

That- Que

​can refer to people or things

¿Dónde está el boleto que compré?

Where is the ticket that I bought?

El hombre que está en la recepción es amable.

The man that is at the reception desk is kind.

Who- Quien, Quienes

refer only to people. used in clauses set off by commas.

Lola, quien es cubana, es simpática.

Lola, who is Cuban, is friendly.

¿Ellos son los niños de quienes me hablaste?

Are they the boys that you told me about?