CSS TYPOGRAPHY Linking Fonts II

Hi, I am just wondering what is the purpose of setting the selector.

https://www.codecademy.com/paths/web-development/tracks/getting-more-advanced-with-design/modules/learn-css-typography/lessons/css-typography/exercises/linking-fonts-ii

qursiont:
3.

Using the selector you just created, set the font to "Space Mono" and add monospace as a fallback font.

code:
space .sample .text {
font-family: “Space Mono”, monospace;
}