What Bitcoin Actually Says About Proof-of-Work

From Section 4: Proof-of-Work

"The proof-of-work involves scanning for a value that when hashed, such as with SHA-256, the hash begins with a number of zero bits. The average work required is exponential in the number of zero bits required and can be verified by executing a single hash."

Key Elements:

Computational search for specific hash patterns

Exponential difficulty scaling Easy verification but hard computation

Economic cost through electricity consumption

λ is to pure as POW is to action.