PingAccess is a policy server so it handles authorization requests in which we can implement all kinds of business logic to validate and authorize the requests.
PingFederate is a federated server so it knows how to authenticate the user and provides an access to a particular resource.
PingAccess provides a way to manage our web application and API in a secure manner. It can be used along with Ping Federate, otherwise we have to implement our own logic to implement the authentication and authorization logic. You can refer the diagram available in this link https://www.pingidentity.com/en/products/pingaccess.html
We have three protocols under the Identity management category.
SAML – Security Assertion Markup Language
OAuth (Open Authorization)
SAML facilitates both authentication and authorization and OpenID is used mainly for Authentication and OAuth is for Authorization alone.
So PingAccess internally uses OpenID for authentication and also leverage Ping
Federate Server which internally uses OAuth or SAML for authentication
I have used CA SAML siteminder federation and also PingAccess in the past. I assume that using PingAccess is somewhat easy compared to Siteminder
Please feel free to add your comments if i misstated anything.