An explanation is a set of statements constructed to describe a set of facts which clarifies the causes, context, and consequences of those facts.
The requirement that an explanation actually clarify the phenomenon under consideration is an important one: simply stated, an explanation of a given phenomenon must be based on better understood phenomena, not less understood ones.
This is why God is not an explanation of anything in reality. Attempting to explain, for example, the origin of human beings by saying that a god created one man out of dust and water and one woman from one of his ribs and that all humans who have ever lived are descendants of these two people, is to "explain" something we know a great deal about — human life — in terms of actions we have absolutely no experience with (the creation of large mammals from dust and water), which contradict other things we know (DNA evidence of common descent, for example), performed by an agent we cannot reliably sense in any way, who, in fact, we supposedly cannot even hope to understand by the use of our own mental faculties (how can mere humans possibly know the mind of God?) — to say nothing of the logically contradictory attributes this purported god is supposed to have (omniscience, omnipotence, and omnibenevolence).