SP receiving a Request in SSO


I am working in a SAML project, implementing SSO to a company’ website. We are working in the Service Provider part.
I have been talking with the Identity Provider part and they told me that we (as SP) are going to receive a when the SSO occurs. But I though that, in SSO, the SP always is going to receive a (not a Request).
Is there any situation (in SSO) that the Service Provider receive a SSO Request?


No. You as the SP will receive a SAML response.

ComponentSpace - 7/18/2019
No. You as the SP will receive a SAML response.

And once we have received the answer, does the SP (our part) have to return something to the IdP? Or what we have to do with the Response?

No. You don’t return anything to the IdP.
The SAML response will include user identity information (eg email address) supplied by the IdP. You use this information to automatically login the user at the SP.
I suggest taking a look at our SAML Primer for an overview of how SAML SSO works.
I also suggest taking a look at our ExampleServiceProvider project which demonstrates supporting SSO as the SP. Its SAML/AssertionConsumerService.aspx page shows how to call the SAMLServiceProvider.ReceiveSSO API to receive and process the SAML response. It then logs the user in locally although exactly how you do this is dependent on your application.
The Examples Guide includes a walk through of the ExampleServiceProvider.