I have a converter that I plug into my USB socket and then I can plug my old style keyboard into this converter. Is that what is being talked about here? The picture looks different.
Not sure what is inside of one of those keyboard adapters, but this is something called a serial adapter (or, more precisely, UART adapter). It is usually used to program microcontrollers (read Arduinos), so everyone dabbling with those (typical audience of hackaday.com) probably has at least one at home, they cost like $2-3.
