In addition to a set of records, we also have a hash of the block.
As you may remember hashing one-way mathematical algorithm used to map arbitrary data (often called the "message") to a bit string of a fixed size, otherwise known as a hash.
The hash of a block can be thought of as a digital fingerprint, and whenever a new block is created, a hash or digital fingerprint of all of the data within the block is generated too.
Now it's important to note that even a slight change to the input data of a hashing algorithm, would result in a drastic change to the output hash. This means that if someone was able to make even a slight change to the set of records stored within our block, the hash of the entire block would change.
As we’ll come to learn, this is a fundamental aspect to the secure nature of the blockchain.