How does Marketing Cloud Connect work, and what are Synchronized Data Sources?

Marketing Cloud Connect integrates Marketing Cloud with a Salesforce CRM org, enabling data synchronisation and Journey Builder triggers based on CRM events.
Configuration: Requires a Connected App in the Salesforce CRM org with OAuth credentials, and the MC Connect managed package installed in CRM.
Synchronized Data Sources: CRM objects are synced to read-only data extensions in Marketing Cloud on a configurable schedule (near real-time for supported objects). Supported objects include: Contact, Lead, User, Account, Campaign, Campaign Member, and custom objects (with configuration).
Journey Builder Salesforce Entry: Contacts/Leads enter a journey when a CRM record meets defined criteria.
Sales/Service Cloud Activity: Journey steps can create Tasks, update fields, or log activity in CRM as a contact progresses through a journey.
Token management: OAuth tokens must be refreshed; expired tokens cause sync failures — monitor via the Salesforce Connector page in Marketing Cloud Setup.