Some of these variants are meant to be used in mathematical notations, where sometimes one font's worth of letters isn't enough to represent every variable in every formula. Although they are not meant to be used that way, people have also used them as a way to put differently-formatted text into places (like some social media platforms) that do not support formatting text. For more information, you can check out this Wikipedia entry.
Unicode also includes enclosed variants of many letters And numbers. Some of these have been given special meaning (blood types, parking symbol) And look different from the others.For more information, you can look at this page.
For use In languages where letters are significantly larger than Latin letters (which we use in English), an additional set of letters, called full-width letters, Is available that Is expanded to the size of that language's letters. For more information, you can look at this page.