Sending text to HX8357 TFT display

I've been messing around with a HX8357 3.5" TFT display, and using the Adafruit_HX8357 along with the Adafruit_GFX libraries to drive it. They can both be found here:

Everything is working alright with the display when using the example code, but I want to start doing my own stuff with it and have a question. When sending text to the display, if you look in the library they simply call the relevant GFX functions to set size, color, position, etc..., then they just use tft.println("Some string") to send strings. My question is, how is this affecting the dispaly when there doesnt seem to be any corresponding register assignment, they just seem to change variable values within the constructor. And I'm not sure exactly what the tft.println("Some string") is doing either. Can anybody shed some light on this for me? Thanks.

Explained here.