Take a visit to the Cypress web site. They ,manufacture such chips so you can take a look at their data sheets.
These chips are no magic. They're microcontrollers with a dedicated program and some integrated interface. USB is mostly a software thing. You need drivers to support these chips, drivers to make the OS think that it speaks to a serial port while the driver goes the USB way, and you need an application that uses these OS calls.
RS422 is a straightforward implementation of UART signals, with one in and one out pair of signals. RS485 is a multidrop version of RS422, a version where many units can a single wire pair. There are no protocol standards for RS485, so for any RS485 application that you have, you must make sure that the additionnal layer of communication protocol (node ID, collision handling, etc.)is supported by every device, otherwise it's a guaranteed crash.