The fallacy of shifting the burden of proof occurs when someone making a claim does not respect their obligation to provide the needed evidence for it, but instead attempts to shift the burden to their opponent.
For example, when someone makes a claim that God is not real, instead of showing why they believe they are correct, they shift their burden of proof to their opponent by asserting that it’s their responsibility to disprove it.
As such, this fallacious line of reasoning is commonly involved with claims that are unfalsifiable, that is, claims that are not possible to disprove. Many religious and supernatural claims that cannot be scientifically proven are examples of unfalsifiable propositions.