2) HTML Tags and HTML Elements

A tag is a bit of text that acts as a point demarcation. To create a tag, HTML gives certain characters special meaning: the angle brackets < and >.
Putting characters within angle brackets creates a tag.
<h1>A heading</h1>

There are two tags: 
Start tag or opening tag and End tag or closing tag. An end tag always matches a start tag, except that it has an extra forward slash after the opening angle bracket.
<h1>A heading</h1>

Element
The combination of a start and end tags define an element. Everything between the two tags is referred to as the contents of the element.
<h1>A heading</h1>