How work Google googleSignIn.silentSignIn ?

Greetings,

About silentSignin…

In oficial doc.

googleSignIn.signIn(clientID, hostedDomain, scopes, listener, serverClientID)

googleSignIn.silentSignIn(clientID, hostedDomain, scopes, listener, serverClientID(optional) )

Both have the same way to use…

What is the diference?

When use  signIn and  silentSignIn?

Best regards.

Sign in brings up a pop up

Silent sign in signs in without a pop up

Sign in brings up a pop up

Silent sign in signs in without a pop up