You can add new measures or dimensions to a Calculated Insight by selecting them from the available attributes list

These are the two dependencies that need to be removed prior to disconnecting a data source. A data stream is a process that ingests data from a data source into Data Cloud. A segment is a group of customers that meet certain criteria based on their data. If a data source is disconnected, any data streams or segments that depend on it will no longer function properly. Reference: [Data Sources], [Data Streams], [Segments]

These are two characteristics of Formulas. Formulas are a feature that allows you to create custom fields in the data model using simple logic on a row-based operation. For example, you can use a formula to create a field that concatenates the first name and last name of an individual. Formulas are easy to use and self-service, meaning that you can create them without coding or complex queries. You can use formulas to enrich your data and create more meaningful segments and insights. Reference: Formulas

Party Identification Id is the only match criteria that is only available as custom in order to perform an exact match in Identity Resolution. Party Identification Id is a unique identifier for each Party Identification record in the data model. It is not one of the standard match criteria that Data Cloud provides out of the box, so it has to be created as a custom match criteria. Custom match criteria allow you to use any field from the data model as a match rule. References: Create Custom Match Criteria

This method should be used when performing aggregations in windows of 15 minutes on data collected via the Interactions SDK and Mobile SDK. Streaming Insight allows you to query and aggregate data from real-time streams using window functions. References:
https://help.salesforce.com/s/articleView?id=sf.c360_a_streaming_insights.htm&type=5