What is traditional blockchain consensus?

Traditional consensus is a linear chain ordering system where every block has exactly one parent block, forming a single continuous sequence. In practice, this means the blockchain grows like a chain of links — each new block attaches to exactly one previous block, and all blocks follow a single ordered line. Knowing this baseline matters because the one-parent-per-block rule is the defining structural constraint of traditional blockchains, and it shapes everything about how they confirm transactions.