Analytics cookies collect information that is used either in aggregate form to help us understand how our Websites are being used or how effective our marketing campaigns are, or to help us customise our Websites for you.
The cookie _gcl_au is used by Google Analytics to understand user interaction with the website.
For example, in order for Google Analytics to determine that two distinct hits belong to the same user, a unique identifier, associated with that particular user, must be sent with each hit.
The analytics.js library accomplishes this via the Client ID field, a unique, randomly generated string that gets stored in the browsers cookies, so subsequent visits to the same site can be associated with the same user.
By default, analytics.js uses a single, first-party cookie named _ga to store the Client ID, but the cookie's name, domain, and expiration time can all be customized. Other cookies created by analytics.js include _gid, AMP_TOKEN and _gac_. These cookies store other randomly generated ids and campaign information about the user.