The argument from ignorance fallacy is where one believe something to be true or false based on the absence of contradictory evidence. This often happens when someone with a claim or position tries to justify their claim because they have no better answer. The claim they believe usually has no evidence for it and is used to fill in gaps of ignorance (lack of knowledge).
Argument from Ignorance Examples
I can’t explain the universe therefore god did it
I can’t explain how life/humans came to be therefore god did it
The above do not mean a god did not do it, and they are not sufficient justifications that a god did do it. The above arguments are simply not sufficient for justification of their conclusions. Better arguments, not fallacious structured, would need to be introduced for any justification of the claims.