Business Login is the process for generating Page access tokens not bound to a User access token. These Page access tokens are dependent on a System User, and so they remain valid through changes in personal accounts. To make these tokens more resilient, they are not subject to an expiration date.
A direct business, a business that holds the ownership of its Pages and apps, can set up a stable Page access token through a System User.
Because business login for direct businesses requires access to the Graph API, it does not offer a login path without ads tracking and measurement.
If your app is supporting Pages that are owned by other businesses, use the Business Login flow. This flow is recommended for direct businesses only.
Before you generate a Page access token based on a System User, you need the following:
/<PAGE_ID>?fields=access_tokenendpoint with the system user access token above.