Networking tools and troubleshooting strategies
Apple has great triage tools to get you to isolate what is failing:


https://support.apple.com/en-us/HT202663
https://support.apple.com/guide/mac-help/use-network-utility-on-mac-ntutl001/mac


One valid item is to use tethering and WiFi as listed in HT202663 - that makes sure your Mac is working with other network connections. That will help guide you in making use of the main Network Utility (the second link)

You’ll just need to make sure DNS works and then see how far your traffic goes from the mac. 


Can it ping the router. 
Does the router see your Mac? 
Does your traffic get past the router to the internet?


In fact, why not start with if you have a green dot in network settings. See the screen shot below and you can click the circle with the ? In it to be guided in help on how to set up your Ethernet.


I would start with that and then post a follow on question showing how far you got and what one step you can’t move forward until you learn something. You don’t need to go through all the networking theory and terms - just enough to get you past one item once you have narrowed down what is failing you.