Blockchain is DeFi’s backbone which makes DeFi decentralized.
Blockchain is a technology/software protocol to transfer digital information (no necessary money) among multiple parties under shared assumptions and data without trusting each other.
More detail on how blockchain works, check 👇
When you try to explain what is a blockchain to Congress, check 👇
https://www.youtube.com/watch?v=pSTNhBlfV_s
The original PoW idea was to fight for Junk Mail through Denial-of-Service-Attack (DDoS) in 1993. But the term Proofs of Work was mentioned in the paper published in 1998.
One possible test run of the blockchain system before Bitcoin is HashCash that invented by Adam Back.
HashCash was eventually failed in 2004 due to a lack of financial feasibility to spend more than preventing spamming emails and waste a huge amount of CPU power after cycle 1,000 times.
Satoshi Nakamoto invented Bitcoin in 2008 through his Bitcoin White Paper that utilized PoW through its trustless and distributed consensus mechanism.
[source](<https://bitcointalk.org/index.php?topic=583.msg11405#msg11405>)
According to Satoshi Nakamoto himself, Bitcoin works only because its valuation has been increased enough to be worth mining for.
[source](<https://blockgeeks.com/guides/proof-of-work-vs-proof-of-stake/>)