What is the difference between having faith in God and believing in God?
A1 Belief and faith, as used in 21st-century English, have overlapping meanings. In fact, in the several dictionaries I consulted, each term is used in part to define the other. But I think we can say that to recognize that God exists, that God is "there," is to believe in God. To recognize that God is "a very present help in trouble" (Ps. 46:1)—is here—means having faith in God.
In Science and Health, Mary Baker Eddy gave us a helpful guide to the usage of these terms (for example, see pp. 23–24, and 297). From this guide, we might envisage a natural progression from a belief that goodness exists and has an impersonal cause, to a faith that this cause will continue to create good. Then comes the fun part. We start finding out more about how and why that cause provides goodness for us and others—how it works. Next we test it. The more we experience the goodness provided, the deeper becomes our faith in its cause.