The PICAXE PWM-IC is a special 8 pin chip designed to drive a L293D motor driver chip to add speed control without any extra output pins needed from your microcontroller.
The PICAXE PWM-IC is meant to be used with a PICAXE chip and an L293D motor driver chip. This IC will allow you to vary the speed of the motors on your robot, or you could use it in other applications like controlling the brightness of LEDs, or adjusting the speed of the trigger on your sentient turret.
A typical application circuit is available on the last page of the datasheet (found under the Resources tab). By sending a Pulseout command (with a PICAXE chip) and entering in a value between 1(slow) - 255(Fast) you can vary the speed of the motors in your application.