This generator lets you convert normal text into cool fancy text that uses a bunch of different Unicode symbols. You can copy and paste the text into your social media accounts including your Instagram bio.
Unicode is an international computing industry standard that specifies all the different characters that ca be used on computers. Unicode was formed in the early 1980s, and at that time computing was significantly more simple, and the internet barely existed. In order to get as many companies on board with the Unicode standard as possible, the organisation needed to pander to all of the companies that they could, so they had to introduce a huge number of character sets to allow for all the uses that all these companies needed.
So all of the fancy "alphabets" that you see above (cursive, bold, italics, etc.) are just different text characters that are in the Unicode symbol set - they're not "fonts" per se, but they do look like fonts.
Unicode is also responsible for creating emojis, since they're actually classed as special text symbols, just like all the other special characters that you see above.
You might notice that when you try to put the symbols in your Instagram posts, that it doesn't work. That's because some websites (Instagram included) removes some special characters from certain parts of the website. But you can still use special symbols in your Instagram bio.