to know robotics you should know these basics:
-mechanical design and theory of machines: some basics in keimatics, gearing, levers and pulleys, chassis and wheels design, metals machining.
-electromechanical and electric actuators like DC, stepper, servo motors, solenoids, relays and their power drivers like H-bridge and PWM technique.
-embedded systems like microcontrollers (PIC still popular don't worry).
-electronics: A/D, D/A, data acquisition systems.
-sensors.
if you know about these topics then you can call yourself know little about robotics, actually I'm sorry but microcontrollers aren't enough to know the necessary fundamentals.
good luck