Connection string describes connection address for a destination like an Internet URL describes a location for a web page.
SAP system's application server
A connection string contains an IP address and a port number. During the recording process, SAP UI node extracts the details of the connection by identifying the Application Server, Instance Number, and System ID of the SAP environment.
Click the icon to modify the connection.
All established connections get listed in the SAP LogonPad. You can provide the Description of connection as Connection String in the Configurations tab of the SAP UI node.