This is a USB-to-serial (5V or 3.3V levels) interface chip that also has the ability to program a PIC32 using PIC32PROG software.

Example circuit from Robert Rozee:

USB/UART mode:
When first powered up, the CG1455 is in USB/UART mode and acts as a simple USB to 5.0/3.3V UART interface.To enter PIC32 programmer mode, press the program select switch briefly, the LED will light.
Pressing the program select switch for greater than 2 seconds will reset the microcontroller on the programming interface but not enter programmer mode. The LED will flash briefly after 2 seconds to indicate success. A "break" command sent from the terminal emulator can also be used to restart the microcontroller on the programming interface (Alt+B in Teraterm).

Programmer mode:
Pressing the program select switch for greater than 2 seconds will exit programmer mode (to go back to USB/UART mode). The LED will go out after 2 seconds to indicate success and when the switch is released the microcontroller on the programming interface will be reset and will switch back to USB/UART mode