on any fieldbus (EthernetIP included), connection is controlled by node that functions as a bus master. one master can talk to one or several slaves.
master is node that has info on partner nodes (slaves).
in case of KRC4, robot can act in several roles. One can use one or more of the roles at the same time:
1x EtherentIP master (standard or not safety rated)
5x EthernetIP slave (standard or not safety rated)
1x Safety slave (safety rated
those five tabs are configuration pages to setup robot as EthernetIP slaves.
this way robot can be slave to multiple masters, and at the same time also act as a master.
for example robot can own some IO to control things like robot grippers etc.
but at the same time, bunch of robots can be slaves to some PLC. this is preferred way to setup things because robot can still be operated with accessories like tools, regardless if rest of the plant is available or not - because robot can control everything directly
another option is to have all IOs controlled by PLC. this is limiting, because using local things like gripper etc would need to send commands to PLC and have PLC forward them to the gripper. so if the PLC is powered off, robot functionality would be limited because use of gripper would not be possible.