Understanding the Use of HTML <hr> Tag

HTML, HyperText Markup Language, is the core building-block of a webpage. It is essentially a set of tags that are used to structure content on the webpage. One such useful tag that HTML provides us is the <hr> tag.

The <hr> tag in HTML is used to insert a horizontal line, or a thematic break, in a document or a section. It represents a shift in content, creating a divider within the text - this could be between topics within a single document or create visual breaks between paragraph elements.

An example usage of the <hr> tag is as follows:

<p>This is some text.</p>
<hr>
<p>This is some other text, separated by a horizontal line above.</p>

Refreshing the webpage after inserting the above code within the HTML document would reveal a horizontal line separating the two sentences.

The <hr> tag does not require any closing tag. It is one of the few self-closing tags in HTML.

Although the <hr> tag is quite simplified, it can be styled using CSS to modify its appearance. For instance, you can change the color, height, width, and even the type of line (dotted, solid, etc.). However, remember that use of <hr> tag is not for applying visual styles but to represent a thematic shift in the content. For stylized separators, it's better to use CSS dividers.

Far different from the incorrect options given in the question (<line>, <br>, <divider>), the <line> tag does not exist in HTML, the <br> tag signifies a line break, not a horizontal line, and <divider> is not valid HTML either, though the name may sound plausible for creating divisions. The correct tag to make a horizontal line in your HTML document is, undoubtedly, <hr>.

Understanding how certain HTML tags like <hr> operate and represent can immensely help in properly structuring and designing webpages. Thus, it's important to be clear on these fundamental components of HTML.