These are the three Data Model objects that Reconciliation Rules operate across. Reconciliation rules tell Data Cloud how to prioritize values for unified individual profiles when there is conflicting information in the data model. For example, if two profiles have different email addresses, reconciliation rules can determine which one to use for the unified profile. Reconciliation rules can operate on the Individual object, which represents a person or entity, the Party Identification object, which represents an identifier such as a social media handle or a loyalty card number, and the Contact Point Email object, which represents an email address. Reference: Identity Resolution Reconciliation Rules

These two requirements are needed when using the Visual Insights Builder to create a Calculated Insight. A dimension is an attribute that can be used to group or filter data, such as product category or customer segment. A measure is an attribute that can be used to perform calculations, such as revenue or quantity. Reference: https://help.salesforce.com/s/articleView?id=sf.c360_a_calculated_insights_create.htm&type=5

A data stream cannot be deleted if any of its attributes are mapped to a Data Model object or used in a Calculated Insight3. These dependencies need to be removed before deleting the data stream.

This is how Data Cloud handles an individual's right to be forgotten. It deletes the individual record from the Individual data model object (DMO) and any related records from the data stream objects (DSOs) that are mapped to it. Reference: https://help.salesforce.com/s/articleView?id=sf.c360_a_data_cloud_delete_individual.htm&type=5

Explanation
The relationship between Individual and Contact Point Objects is 1: Many. This means that one Individual can have many Contact Points, such as email addresses, phone numbers, or postal addresses, but each Contact Point can only belong to one Individual. References: Data Model Overview