The Google CLS Score is a measure of how well your site's layout conforms to best practices by taking into account the distance between elements on each page and their relative impact. What this means in terms you can easily understand, however, is that it will score higher if there are more navigational links or any other information users would need right at hand as opposed to making them scroll down for what they're looking for. The farther away something appears from where people start scrolling on the screen or when there aren't navigation buttons directly next to content readers want access to.