[Term] Identity provider security token service or relying-party security token service [Definition] 
A software component or service that is used by an identity provider to accept tokens from a federation partner, and then generate claims and security tokens on the contents of the incoming security token into a format consumable by the relying party. A security token service (STS) receives security tokens from a trusted federation partner or claims provider STS. Then, the relying party STS issues new security tokens to be consumed by a local relying-party application.