What does the clear property do?

The clear CSS property sets whether an element must be moved below (cleared) floating elements that precede it. The clear property applies to floating and non-floating elements.

When applied to non-floating blocks, it moves the border edge of the element down until it is below the margin edge of all relevant floats. The non-floated block's top margin collapses.

/* Keyword values */
clear: none;
clear: left;
clear: right;
clear: both;
clear: inline-start;
clear: inline-end;

/* Global values */
clear: inherit;
clear: initial;
clear: unset;

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