The Pega Robotic Automation Security Token Service (STS) is a web service that can be hosted in Internet Information Services (IIS). It serves as a minimalistic version of Active Directory Federation Services (AD FS) for authenticating the Pega Robot Runtime and Pega Robot Studio products with Pega Robot Manager. STS uses the domain user credentials of the user's Windows session.
Using the Robotic Automation Security Token Service (STS) lets you avoid the per-seat licensing cost of Microsoft's AD FS. By default, STS uses the name@domain or name of the user logged onto the machine, but it can optionally provide a secure token provider for authentication purposes using your Active Directory (AD) or Lightweight Directory Access Protocol (LDAP) user store.
For more information, see the following documents: