The proper answer may be "none", since Stack Exchange sites are for the most part not learning sites.
Most question you could have about networking basics are already answered somewhere on the Internet. So the first thing to do is to perform some researches including (but not limited to) the Stak Exchange network
Each S.E. site has its own policy regarding which type of question can be asked, so you'll to check the help center of some of them to determine if your question fit.
Concerning this S.E. site , I.E. network engineering, educational questions are explicitly off-topic. (see What topics can I ask about here?)
However when the questions are specific enough, properly formatted, show some research and are relevant to the field, they often get an answer.
Edit: you can also try the chat where you may find help about questions that are otherwise out of topic on the site itself.