Hello Whandall! It is ONE display with TWO objects, disp1 and disp2. Objects are created by calling constructors:
Adafruit_SSD1306 disp1(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
Adafruit_SSD1306 disp2(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET, clkDuring);
As you can see, main difference is parameter clkDuring, which tells the Arduino on which frequency I2C bus should work.