The <i> tag is used to define a part of the text in a different voice. The text placed within the <i> tag is usually displayed in italic. This tag is used to define technical terms, phrases from foreign languages, etc.
The <i> tag is an element of a physical markup, that is, the embedded text differs only visually and is not perceived as important by browsers and search engines.
If you want to highlight the important text then instead of the <i> tag, use the semantic markup tag <em>.
The <i> tag comes in pairs, so the closing tag is required.
<html> <head> <title>Title of the document</title> </head> <body> <p>Before the end of the week <i>it is vital to</i> finish all the work.</p> </body> </html>