HTML commands are called TAGS and they usually come in pairs. 
They are enclosed in these funky arrows:  <  > 
This is the basic structure: 

<tag>                        </tag> 

The computer reads anything inside the arrows as a command. 
It reads the above structure in this way... 
<do this>                <stop doing this> 

The forward slash / tells the computer to stop doing something. 
So, for example, 
<b>                   </b> 
the above line of code tells the computer to start "bolding" and then to stop "bolding". 

Anything in an HTML document that is NOT inbetween those arrows, the computer reads as "content" and it displays it, as is, in the browser window. 
These are the basic tenets of HTML coding. 
You're essentially half-way there!