What is 'Preimage of Block'?

When we say about preimage of block, what does it exactly mean?

The data inside of block? (ex. each transaction, any input to change some state)

Thank you in advance.

No idea. In general, a “preimage” is a value D such that hash(D) matches some given hash value. In a block this could likely refer to block data or the parent block.

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Thank you, so it would depend on context.