The <s> tag is used to define a text, which is not relevant any more. Browsers display the tag content as a strikethrough text.
For example, the tag can be used to show new price of the product, whilst still displaying its original price but with a line through the middle.
Don’t use the <s> tag to define a deleted text, use the <del> tag for that purpose.
The <s> tag comes in pairs; the content is written between the opening (<s>) and the closing (</s>) tags.
<html> <head> <title>Title of the document</title> </head> <body> <p><s>I am studying in high school.</s></p> <p>I am studying in an university.</p> </body> </html>