These two steps are required when configuring a Marketing Cloud activation. You need to select an activation target that represents a Marketing Cloud business unit and a contact point that represents a Marketing Cloud data extension. Reference: https://help.salesforce.com/s/articleView?id=sf.c360_a_data_cloud_marketing_cloud.htm&type=5

These three out-of-the-box connectors are available for Data Cloud. They allow you to ingest data from Marketing Cloud, B2C Commerce, or Amazon S3 into Data Cloud and map it to the Data Cloud data model. Reference: https://help.salesforce.com/s/articleView?id=sf.c360_a_connectors.htm&type=5

Reconciliation rules are used to select attributes for Unified Individuals when there is conflicting information in the Data Model. Reconciliation rules can use different methods to prioritize values, such as source sequence, most recent value, or most frequent value. For example, if two profiles have different first names, reconciliation rules can determine which one to use for the unified profile based on the source sequence or the most recent value. Reference: Identity Resolution Reconciliation Rules

The Source Sequence reconciliation rule allows you to sort your data sources in order of most to least preferred for inclusion in a unified profile9. For example, you can specify that data from Marketing Cloud should have higher priority than data from Service Cloud when selecting attributes such as first name or last name.