An IdentityProvider (formerly a Shibboleth origin) is a deployment of SAML software that authenticates users and issues authentication and attribute assertions to relying parties, typically ServiceProviders.
In Shibboleth, the IdentityProvider software is in Java, and is provided as a package of Java servlets and configuration files that manages the issuing of assertions and obtains attributes from enterprise directory and database stores. Apache is required in most cases to handle the authentication of ServiceProviders using mod_ssl. Tomcat is the recommended and supported servlet container.
UserAuthentication is currently not part of the software, and is handled by the web server or servlet container. Eventually, some support for authentication will probably become part of the software in order to support th feature set of SAML 2.0