Clearing cookies does not delete passwords or passwords that you've saved.
Passwords are often stored separately in the browser's password manager.
But if you clear the browser's data by selecting the "passwords" option within the clearing data menu, such as in the Chrome browsers settings then the saved passwords will be deleted.
To avoid deleting your passwords when clearing your browsers data, be sure to deselect the password option and only clear the cookies and cache.
What clearing cookies does is logs you out, resets website preferences and can make websites load slower.
When you clear cookies it logs you out of websites that you're currently signed into because the cookies contain your login session information are removed.
Clearing cookies also resets websites preferences, which mean that you may have to re-enter your preferences on certain sites.
Clearing cookies also can make websites load slower as the browser has to also re-download some assets it previously stored in the cache.
To avoid deleting saved passwords open the browser settings and find the section for clearing of browsing data.
And look for an option which separates the cookies, cache and the browsing history and passwords.
And ensure the checkbox that is next to the "Passwords" is NOT selected.
And only select "Cookies" and any other desired data you want to clear and then confirm and clear the selected data.