The PCB's or just IC's are designed to work with a microcontroller this is normally ByPic, Arduino or Raspberry Pi. They will have an I2C, serial or both interface. A PC can also be used by using a USB to serial or USB to I2C converter depending on which interface is required.

I2CN12 (NEW) I2C to Serial Bridge to add an extra UART to a microcontroller when only I2C is available.
I2CN20 I2c Real Time Clock Power down, so that microcontrollers can consume zero power for long periods

P0 Series (I2C or Serial) These are pre-programmed microcontrollers that can expand the current microcontroller offering or give protection to the existing microcontroller pins.

PO15 GPIO with PWM
PO17 LCD Back Pack chip

Adruino Touch (I2C Only) - specifically for the Arduino, gives a user interface via a touch pad and 16x2 lcd display
BV4212 128x64 (I2C Only) LCD screen and a rotary encoder for input, this can be easier to use than touch buttons
BV4242 (I2C only) Exactly the same as the Arduino Touch but designed for other microcontrollers as well.
BV4243 (I2C Only) Is a 16x2 LCD with touch keypad. This is unique in that it can take the standard Blue/Green..etc. LCD or the RGB LCD that has three back lights and can produce many colours.
BV4244 (I2C Only) Similar to BV4243 but this can take a 20x4 LCD display
BV4612 (I2C and Serial) A comprehensive but larger user interface, 126 x 64 LCD screen.
BV4601 (I2C and Serial) This can be stacked with another or with the motor controllers. This device also has 2 ADC inputs.

BV4603 and BV4604 Motor Controllers (1A and 4A, I2C and Serial). These can be stacked, suitabe for stepper and DC motors.