What is data enrichment?
Data enrichment is adding information to a record from sources outside it, so the record describes its subject more completely than it did when you received it. The input is a partial description of something real, a person, a company, an address, a transaction, and the output is that same description with more of it filled in and checked.
The reason it exists is that records almost never arrive complete. A form fill gives you an email and nothing else. A conference badge scan gives you a name and a company. A LinkedIn export gives you a profile URL. A transaction gives you a postcode. None of those is enough to route the record, score it, or act on it, and every one of them is enough to find the rest, because the missing facts already exist somewhere outside your system.
The distinguishing word is outside. Computing a value from fields you already hold, deriving a lead score from a title and a headcount you already have, is a transformation rather than an enrichment. Enrichment brings in a fact you did not have and could not have derived, which is also why it is the only data-quality operation that costs money per record.
It is a process rather than a project, because the underlying facts move. People change jobs, companies rename, domains retire, and a record that was correct at import is a slightly worse record every month afterwards. The useful question about any database is not whether it was enriched but when, and against what.