I need to know what the little "thing" that i marked in blue is and how it works.
picture taken here: https://www.sparkfun.com/products/13282
It's most likely a decoupling capacitor meant to smooth out the voltage supply to the internal control chip.
This is standard practice to add to any chip. Power cables create a small bit of parasitic inductance in relation to the area between the lines. This inductance can induce voltage spikes when current draw changes significantly. A capacitor shrinks the effective area between the power lines.
This is also why the general advice for decoupling capacitors is to put them as close to the chip as physically possible.
It's a capacitor connected between 5V and GND and it smooths out voltage spikes for a cleaner power supply to the chip. A cleaner power supply means the circuitry in the chip can more easily pick out the data signal (i.e., the reference voltage is more constant, so the actual signal appears more stage.)