What is the difference between OCAPI Shop API and OCAPI Data API?

OCAPI (Open Commerce API) has two primary document types serving different purposes:

1. Shop API — the customer-facing storefront API for product search, category browsing, basket management, checkout, and customer account operations. It operates in the context of a shopper session or guest token. Used by the storefront frontend or headless clients acting on behalf of a shopper.
2. Data API — the back-office integration API for reading and writing product catalogs, orders, customer profiles, inventory, and site configuration. It requires Business Manager user credentials or a client credentials grant and is not intended for direct shopper interactions.

Both APIs use REST + JSON and OAuth 2.0 authentication, but their access scopes, permissions, and intended consumers differ significantly. Mixing up Data API and Shop API endpoints is a common mistake in integrations.