Hi Mohan,

Flow is a powerful business automation tool that can manipulate data in Salesforce in a variety of ways. Such an application can be created right from the org’s setup with just drag-drop/point-click. The ease of creating flows makes it the number one go-to tool when it comes to complex business requirements. It is not only easy to create but also it does not require any coding. Beware! That does not mean you don’t need to know the Salesforce platform’s object relationships and overall how Salesforce runs. You have got to have (at least) mid-level understanding of SFDC and its features in order properly use flows.
It uses some variables in order to store the values so the "Recipient Id" and "Target Id" are the variables that store the values.
Please refer to the following links as they might provide you with more information about the Lightning flows.
https://www.salesforceben.com/introduction-salesforce-flow/
https://help.salesforce.com/articleView?id=flow_ref_resources_variable.htm&type=5
https://help.salesforce.com/articleView?id=flow_ref_resources.htm&type=5

I hope you find the above solution helpful. If it does, please mark as Best Answer to help others too.

Thanks and Regards,
Deepali Kulshrestha