The term is broader than help center. A help center is the part customers see. A knowledge base can also hold internal notes: which supplier handles returns, what to do when a payment fails twice, which discount a long-time customer may get. It can live in a helpdesk, a wiki, shared documents or a folder of notes.
Why it matters
Support quality depends on how easy it is to find the right fact while writing a reply. When the knowledge sits in one person’s head, answers change with who is on duty. A written knowledge base makes answers consistent, speeds up new teammates, and gives AI drafting tools something reliable to work from. Tools that write replies from your own material are only as accurate as that material, which is what grounding means.
An example
An internal page lists the three reasons a subscription renewal can fail and the reply for each. Whoever answers the email checks the page instead of asking a colleague.