A breakout board is a small PCB used to give quick access to the component pins. It makes prototyping easier by creating module of component that can be reused on breadboards. Not a lot of components are compatible with breadboards, some chips don’t come in DIP format, potentiometers, encodes or keyboard switches are made for attach directly to a PCB and cannot be mounted on a breadboard directly.
USB-C breakout board

Adafruit-USB_Type_C-Breakout_Board-4090-datasheet.pdf
Potentiometer
Sturdy Pots by Paul Stroffregen