Hi architg36409633
Data sources in audience manger are name spaces that helps you organize your data.They are used for:
1.Data collection
2.Identifying users
3. Synching Ids
4.Merging profiles
When the data source is setup as "Cookie" then data will be collected and associated with a profile based on identifier stored in browser cookie.
When the data source is setup as "Cross-device" then data will be collected and associated with a profile based a customer-provided, authenticated ID.
Data source selection in case of rule based traits will not hamper the trait qualification,as they will be qualified on the basis real time website data.To better organize our data and associate the correct profile with the data collected,we need to make sure we are choosing the required data source.For more information on data source creation,please refer to doc here.