Dripcap is a simple Electron-based tool which captures and displays your network traffic.
The program doesn't require installation or any third-party components. Just unzip the download and it's ready to run on 64-bit Windows, Linux or Mac.
You can start a new capture session in a couple of clicks, and Dripcap immediately displays basic details on your network traffic: type, source and destination IPs and packet length.
Clicking any packet gives you a low-level breakdown: time stamp, MAC addresses, source and destination ports and assorted other IP and TCP-related information.
There's also a hex and text view of the packet contents, which may contain URLs, logins, or other clues to its purpose.
Filters allow you to restrict the packets you see, handy if you need to tune out the noise. You do this by typing text rather than selecting options from menus, but it's not difficult. You could type just tcp to show only TCP packets, for instance, or payload.length > 80 to display packets with a payload... (You get the idea.)