Lot numbers can typically be found on the outside of packaging.
[1] The lot number enables tracing of the constituent parts or ingredients as well as labor and equipment records involved in the manufacturing of a product.
This enables manufacturers and other entities to perform quality control checks, calculate expiration dates, and issue corrections or recall information to subsets of their production output.
It also gives consumers an identifier that they can use in contacting the manufacturer and researching the production of goods received.
For example to trace back the origin of fish or meat, in case of a public health problem.