Using Superscript and Subscript in Excel -
A Tutorial Video

It’s when you are using small letters or numbers that are attached to the top of the regular sized letters.
For example, when writing ordinal numbers, such as 1^st, 2^nd, 3^rd etc, or when you mention powers in math such as 2⁸.

Subscript is the same but with letters attached to the bottom.
For example with chemical formulas: H₂O, or when mentioning number bases in math: 64₁₆.

Formatting the text as superscript or subscript goes as follows:

1. Write the text as usual, with regular sized letters, and press Enter.
2. Now double click inside that cell, and carefully select the characters to become superscript.
3. Right click inside your selection, and choose "Format cells…" (or use the shortcut keys: Ctrl+1)
4. Check the "Superscript" box and click OK.
5. Now click outside the cell, and you're done