To actually believe in the existence of God requires faith. To merely say that you believe God exists does not. Ask a religious person, "Do you believe God exists?" and they will almost definately say, "Yes" but if you were to also ask them, "Why do you believe God exists?" Their answers would reveal who truly believes in God as a matter of faith and who "believes" in God because they think that is the "correct" answer to the question.
Thanks to the bigotry of Anti-Theism and the confusion about the distinction between Atheism and Anti-Theism, I would not be surprised to learn that many people who claim to believe in God only do so because they have been indoctrinated to believe that anyone who does not believe in God (Atheist) opposes God and hates religion (Anti-Theist). So while they may not actually have faith, while they may not actually believe in God, they know they do not hate God or religion and simply pretend so as not to be considered part of the bigotry wrongly associated with Atheism.