A company's external applicationis protected by Salesforce through OAuth.

To limit the level of access to the data of the protected resource in a flexible way, the identity architect should create custom scopes and assign them to the connected app. Custom scopes are permissions that define the specific data that an external application can access or modify in Salesforce. Custom scopes can be created using Apex or Metadata API and assigned to a connected app using OAuth 2.0 or SAML protocols. Custom scopes can provide more granular control over data access than standard scopes, which are predefined by Salesforce. References: Custom Scopes, Create and Assign Custom Scopes