The Source and Destination settings are used for applying filters to network traffic, which give you a way to narrow down the traffic that you are monitoring or manipulating. Here's how they work:
Source. By setting a source, you are instructing the software to consider only the packets originating from the specified source IP address(es). This can be particularly useful if you are only interested in monitoring traffic from certain devices or networks. For instance, if you only want to track packets coming from a specific server, you would set the source to the IP address of that server. Any packets not originating from that address would be ignored by the filter.
Destination. By specifying a destination, you are telling the software to consider only the packets sent to the specified destination IP address(es). This can help you focus on the traffic going to a certain device or part of your network. For example, if you want to monitor all traffic going to a specific client machine or a group of machines, you would set the destination to the IP address(es) of the machine(s). Any packets not destined for the specified address(es) would be ignored by the filter.