What is subscripted and superscripted texts mean?

Answer 1

H2O => 2 should be subscripted (below).
x square => 2 should be superscripted (above).

Answer 2

superscripted text is a text which is above text line, for example we can use it for writing units for volume or areas.
subscripted text is a text which is under text line, for example we can use it for writing chemical formulas.
I hope that I was clear enough.

Answer 3

subscripted text is a text that you want to make appear a bit below the normal baseline..
ex:- <h1>Dheeraj _Reddy</h1>
here,Reddy will appear a bit below of Dheeraj.

superscripted text is a text that you want to make appear a bit above the normal baseline..
ex:- <h1>Dheeraj ^Reddy</h1>
here,Reddy will appear a bit above of Dheeraj.
here's a code example:-
https://code.sololearn.com/W0WfKb4yLX7j/?ref=app