I know that the blow red encircled component is the 16MHz Crystal Oscillator (XTAL):
But PB6 and PB7 pins are called XTAL1 and XTAL2 pins which are not accessible by the Arduino board.
Are these pins where the 16MHz crystal oscillator is connected. But if so why are they two of them? I searched net but couldn't find explicit information about these.
How many clocks in total this board have?