A blockchain is a continuously growing list of records, called blocks, that are linked and secured using cryptography. Blockchain is a type of Distributed Ledger Technology (DLT) in which transactions are recorded by following consensus algorithms and peer-to-peer (P2P) computer networks. The ledger is immutable, reliably replicated across distributed computer nodes and deterministic.
Blockchain collects different information in a group, known as blocks. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data. Every newly generated block is connected to the previous block which forms an endless chain of blocks known as the blockchain.
Genesis Block is the first block that doesn't contain the previous block information on the blockchain. The first recorded block is recorded and hardcoded in the software on its respective blockchain network. Sometimes, they are referred to as Block Zero (Block 0) or Block 1.
From the genesis block to the most recent block, the total number of confirmed blocks is referred to as Block Height. They are calculated from the launch of the blockchain network. The genesis block is the first-ever block, so it has a block height of #0, and the first mined(validated) block is #1. It is also used to check statistics of a copy of a given blockchain is up to date with other global blockchains of its respective network.