Subscript is a formatting element used to make text downward and is used to write formulae either chemical formulae or mathematical formulae. You can write any value having downward direction by using subscript tag
<sub>Content</sub>
Or
<tag><sub>Content</sub></tag>
You can apply subsript element to any element and use any where within a HTML document.
Subscript is a pair tag and output of subscript element is downward text like you can see in above example.
Open notepad or any other text editor, follow the following points.
I love Desiningto heading 3
I lovetext
save file with name task.html or task.htm and then open it using any browser and see results.
Don't forget subscript is non empty element which means it always comes in pair.