Payment Vault & Tokenization — Stores payment credentials as secure tokens so cards and bank details never touch your systems in raw form, shrinking PCI scope. Checkout and the billing portal write to it; payment runs, retries, and auto top-ups charge against it.
Payment Vault & Tokenization lives in the Rate & Bill phase of Fulfill & Bill — the stage where you activate what was sold, meter what's used, bill it right. In the corpus tool index this phase maps to the Billing and Paymentscategories.