Authorization is the function of specifying access rights to resources such as APIs. More formally, "to authorise" is to define an access policy where access requests are approved or disapproved. So, Access Keys are used for this purpose.
Here, the key which is auto-generated is associated with the user selected, once it is enabled. Anyone can use this access key but can access only those APIs of which the selected user has the permission to access based on his role (admin/seller/user...etc.).
How to use the access key to access any API?
You can use this access key to access APIs via StoreHippo node-js SDK. For this, you can refer to - Storehippo SDKs. Also, here is an example below of how to use this auto-generated access key to access products listing API: