Answer 1

The <em> tag is a phrase tag. It renders as emphasized text.
https://www.w3schools.com/TAGs/tag_em.asp

The <span> tag is used to group inline-elements in a document.
The <span> tag provides no visual change by itself.
The <span> tag provides a way to add a hook to a part of a text or a part of a document.
https://www.w3schools.com/TagS/tag_span.asp