How are blocks connected in a traditional blockchain?

In a traditional blockchain like Bitcoin, every block has exactly one parent — the block that came directly before it. Each new block contains a reference to its parent's unique fingerprint (called a hash), which locks the two blocks together. The only exception is the very first block, called Genesis, which has no parent. From Genesis forward, every block chains back to it in an unbroken sequence, all the way to the most recent block at the tip. This single-parent, linear structure means the history of the chain is easy to follow — but it also means only one block can be added at a time.