Super Saiyan Blue
Super Saiyan God is a form that empowers the user with God ki and the ability to sense God ki. This form is supposedly more powerful than Super Saiyan Blue, though that is up for debate. The form’s most frustrating feature is that it has a time limit.
Now, Goku was the first Saiyan to harness Super Saiyan God in many years, so not even the Kais knew about it. That’s how rare the form was. Then Super Saiyan Blue was discovered by Goku and Vegeta, as in nobody had harnessed that form before them.
After using Super Saiyan God, Goku absorbed some of that god ki and infused it into his Super Saiyan form.
In conclusion, Super Saiyan Blue is just a Super Saiyan infused with God ki.