What is the flex-wrap property used for?

The flex-wrap CSS property sets whether flex items are forced onto one line or can wrap onto multiple lines. If wrapping is allowed, it sets the direction that lines are stacked.

flex-wrap: nowrap; /* Default value */
flex-wrap: wrap;
flex-wrap: wrap-reverse;

/* Global values */
flex-wrap: inherit;
flex-wrap: initial;
flex-wrap: unset;

Source: https://developer.mozilla.org/en-US/docs/Web/CSS/flex-wrap