Урок 45. Относительные местоимения. Часть II. Lesson 45. Relative Pronouns. Part II.

As well as being interrogative prionouns,  что (what) and ктo (who) are also used as relative pronouns.
(А) Что is used as:

Урок 45. Относительные местоимения. Часть I. Lesson 45. Relative Pronouns. Part I.

Который is a relative pronoun which is used after nouns to mean who, which, that.
(А) Russian uses the adjective который as a linking word between parts of the sentence to indicate who, which, that.For example: The young man is skiing. The young man is thе former world champion.