Clarification Sites
These sites are nice at providing clarification to many different technical aspects within cybersecurity:
Command Line Reference - Great for getting the hang of different CLI's(Powershell, Linux, MacOS) all in one place; is similar to explain shell
Explain Shell - Tells users what commands, syntax, and phrases do strictly in linux. Unfortunately, does not explain definitions of some of these terms outright (IE: sudo == "Super User Do")
W3 School - Easily one of the best resources for clarification on statements, arguments, and other keywords with any programming languages that they provide with examples showing proper syntax and formatting. Immediate bookmark in my opinion.