API Access Keys allows users to pull information from PagerDuty and gives you access to the REST API at the account level. Only PagerDuty account owners and administrators have access to them.
Users who do not have this access can still create their own API User Tokens from their user settings page. The difference is that these particular tokens are tied to their user account, which gives them access only to their current level of permissions. More information on API User Tokens on our developer site here.