What is an individual block in a blockchain, and how do you recognize it?

"An individual block within a blockchain is simply a record that contains data. These records relate to each other through an encrypted communications channel. Blocks are immutable and cannot be changed once they are written. Blocks are identified based on their height and header hash. A computerized algorithm known as a hash function is used to identify individual blocks. The blocks are stored in distributed flat-file databases across many different computing platforms."