First-party Cookies are created by a visited website. They can be used by the website owner to gather analytics data, for content personalization, remembering language settings, and other functions that ensure a better user experience.
Check out our Free Online Cookie Scanner: https://piwik.pro/cookie-scanner/
More about First-Party Cookie and Data on Piwik PRO Blog:
First-Party vs Third-Party Cookies: Why First-Party Is the Way to Go