I am following this Adafruit tutorial on 16x4 LCD, and I managed to make it work. https://learn.adafruit.com/drive-a-16x2-lcd-directly-with-a-raspberry-pi/wiring
From this tutorial, the potentiometer for the LCD contrast (3rd pin) is also connected to the 5V? Why should it be like that? it still worked the same when I disconnect it. I also tried directly connecting it to GND with 10K resistor, and it worked well.
It's really confusing for me as I just starting out playing with electronics.