What aspects of knowledge should a webmaster understand?

Recently, there are more and more new webmasters around me. Today, Xiaozijie will chat with you about the most basic things. As a webmaster, what knowledge should we learn and what aspects of knowledge should we understand? I believe that after reading Xiaozijie's article, everyone will gain a lot. With the Internet entering the Web 2.0 era, more and more friends have started to consider building their own websites.