FT232 is USB to serial port adapter chip. Typical application of these chips is anything that has to be connected to USB but does not warrant full-featured USB implementation. This includes various interface cables and converters, (low-cost or specialized) test and measurement equipment and large amounts of various (semi-)custom electronics (both hobbyist and industrial).
In essence, FTDI's chips are the go to solution for adding USB support when you don't want to spend too much time on it. I would argue that today there are better and cheaper alternatives, but FTDI was probably the first vendor of such chips with reasonable documentation and software support.