Part 4/9:
In contrast, many other systems labeled as "blockchains" do not utilize proof-of-work, and their guarantees of immutability are far weaker or nonexistent.
The Difference Between Distributed Ledger Technology and Open Blockchains
Andreas distinguishes between Distributed Ledger Technology (DLT) and the open blockchain concept exemplified by Bitcoin. Many systems market themselves as blockchains but do not employ proof-of-work or open, permissionless participation.