This is a A4988 Stepper Motor Driver with Translator and Overcurrent Protection
This stepper motor driver is used to control one bipolar stepper motor at up to 2A output current per coil. 
key features:
Simple step and direction control interface
Five different step resolutions: full-step, half-step, quarter-step, eighth-step, and sixteenth-step
Adjustable current control lets you set the maximum current output with a potentiometer, which lets you use voltages above your stepper motor’s rated voltage to achieve higher step rates
Intelligent chopping control that automatically selects the correct current decay mode (fast decay or slow decay)
Over-temperature thermal shutdown, under-voltage lockout, and crossover-current protection
Short-to-ground and shorted-load protection
 
Data Sheet: