Why should we tag <del></del> to deleted the words or sentences? Can't we just press backspace on it?

Answer 1

<del></del> tag used to show a strike through on selected word. you can delete the words by pressing del or backspace but using <del> tag is an easy way to show the user that you have modified something. but over use of this tag can make your page irritating and unreadable. it is just to express little amendments.