Unicode is an international not-for-profit o that started in the 1980s as an effort to "unify" the "codes" for textual characters used in the computing industry. "code", I just mean a number. Computers only understand numbers, and so you need to tell the computer which number refers to the letter "a", which one refers to the letter "b", etc. so that you can them on a computer screen (otherwise you'd be reading ones and zeros right now). So the problem in the 1980s was that there wasn't a universally agreed-upon set of "rules" for which number refers to which character, and so every programmer was writing their own set of rules, and whenever their programs interacted with programs written by other programmers, they'd need to make specially designed "translators" to allow the programs to communicate. Unicode sought to solve this by creating an international standard - meaning that everyone would be using the same number-to-letter "rule book".
Okay, so how does this relate to generating small text? Well, as it turned out, there were a bunch of people that weren't too interested in Unicode. They had specific character requirements that Unicode hadn't accounted for in their initial specification. So in order to get programmers and to adopt the Unicode standard faster, Unicode began a bunch of weird symbols and rules that those people needed for their applications, and thus Unicode's full character set exploded to include include tens of thousands of different symbols, for many languages, and many arcane legacy systems.
Along the way, it picked up a set of symbols which can be used to emulate "small caps" (an alphabet of small capital letters), and a somewhat incomplete set of subscript and superscript characters. So the small text letters that you see in the output box above are just a few of the 130,000+ symbols that are specified in the Unicode standard - just like the symbols that you're reading right now.