Connection
A Connection (pushtopics__Connection__c) defines the authentication configuration used to connect to a Salesforce org. A Connection can act as:
A Source for retrieving data
A Target for performing actions
Authentication Flow
Data Sync Pro handles authentication through two paths, decided at runtime based on the Is Current Org flag on the Connection record.

Current Org: Runs as the currently logged-in user, requiring no additional credentials.
OAuth 2.0: Authenticates through a Named Credential using an OAuth access token. Two flows are supported for obtaining the token:
Client Credentials Flow — no interactive login; the connection runs as the Run As user specified on the External Client App.
Refresh Token Flow — requires a one-time interactive login; the connection runs as the user who authorized it.