Question on html

Question

Hi everyone, hope you're having a great day.
I have this question about html, I took a beginner and intermediate course on Mimo app, and then started learning it on sololearn from the beginning, and I found some changes, for example:
1.using <hr> instead of <br>
2.using <img src="/> instead of <img src=">
Can someone please explain.

Answer 1

1.
I think some tags are used to modify semantics, and some tags are used to decorate the page.

The following content is copied from other sites.

https://html.spec.whatwg.org/#the-hr-element
The hr element represents a paragraph-level thematic break, e.g. a scene change in a story, or a transition to another topic within a section of a reference book.

https://html.spec.whatwg.org/#the-br-element
br elements must be used only for line breaks that are actually part of the content, as in poems or addresses.

2.
https://html.spec.whatwg.org/#void-elements
void elements (elements that have no end tag in the HTML syntax).
area, base, br, col, embed, hr, img, input, link, meta, param, source, track, wbr

http://xahlee.info/js/html5_non-closing_tag.html
Is the Ending Slash Optional?
HTML5: the slash is optional.
HTML4: the slash is technically invalid. However, it's accepted by W3C's HTML validator.
XHTML: The slash is REQUIRED.