Block Height

Block height is the number of blocks between a given block and the very first block, known as the genesis block. The genesis block is height zero, the next is height one, and so on. Block height is the simplest way to describe how far a node has synced: you compare your node current height against the network tip reported by a public explorer, and when the two match you are fully synced. Height is also how the protocol schedules events such as reward changes. Tracking height rather than a rough percentage is the most reliable way to judge sync progress, since recent blocks can be slower to verify.