This key is a Universally Unique Identifier (UUID) and you pass it in the
key parameter each time you make a call to us. Put simply, it allows us to retrieve the correct configuration for you.
It is recommended you store the key rather than hardcode it into your website, allowing you to configure a different one should you need to.
For billing purposes, we count the number of requests to our service that include your key. You may wish take this information into account when deciding on your integration type. Integrating the API on the client side, via AJAX will expose this key.