It's almost like a bunch of building blocks from a lego set. These building blocks are called HTML tags. More often then not HTML tags not only have a beginning tag but also a counterpart, thus whatever between these 2 would be effected. The beginning tag marking the beginning of the effect and the counterpart marking the ending of the effect. An HTML counterpart is called the ending tag.
Some specific tags have attributes which are marked after the name of the tag.
These attributes help to specify exactly the effects of the tag. Just go on to chapter 1. and start learning the basic tags, and it will eventually start making more sense. First of all lets break down the entire address your browser reads when going to a website. You've probably also stumbled onto an address which hadn't defined a page yet it still loaded something. This is because you were loading the main page of that directory.