One may have reasons for believing certain things, and these reasons may also be explanations for believing them, as in when one wants to believe what is true. On the other hand, one may give reasons why, that is, he believes that God exists or that a certain kind of act is wrong. One may justify his beliefs. He may, for instance, have had certain experiences or needs that caused the belief. These would explain the belief.
Explanations have to do with causes.
Scientific explanations are scientific laws, hypotheses, or theories. The laws, hypotheses or theories are the explanation. This substance is copper. If the part of the explanation is only probably true, the explanation is probable. The generalization need not be empirical.