There is a difference between knowing and believing.
There is a difference knowing you will do well in you exams and believing you will do well in exams.
Knowing means you understand the questions/theories/keynesian/monetarism/marxist economists/capitalism inside out.
Believing means you feel that they are real but they may not be real and beliefs can be subjective.
The same concept applies to God.
Do you believe or know God today?