HELP with microcontroller MK10DN512ZVLL10

Hi,
you've had time to guardre program. In practice, does is to blink an LED, after you press a button records the temperature leaving the LED lit and shows. Only I did not understand some instructions first. I have some basic questions ...
For example:

PORTB->PCR[11] = PORT_PCR_MUX(1);

BITBAND_REG(PTB->PDDR, 11) = 1;  // output

PTB->PSOR = (1u << 11);  // output = 1, vreg enabled

There is a particular reason because it uses PDDR?

I see in the program of MICRO other GPIO Register Masks. It would have been equal usarne another? And the 17? And (1u<<11)?

What do this?

#ifdef STDIO_UART1

static uint8_t stdio_buff[80];

static ring_buffer stdio_ring_buffer;

#endif

PORTA, PORTB, PORTC what gate is??

Hi,
you've had time to guardre program. In practice, does is to blink an LED, after you press a button records the temperature leaving the LED lit and shows. Only I did not understand some instructions first. I have some basic questions ...
For example:

PORTB->PCR[11] = PORT_PCR_MUX(1);

BITBAND_REG(PTB->PDDR, 11) = 1;  // output

PTB->PSOR = (1u << 11);  // output = 1, vreg enabled

There is a particular reason because it uses PDDR?

I see in the program of MICRO other GPIO Register Masks. It would have been equal usarne another? And the 17? And (1u<<11)?

What do this?

#ifdef STDIO_UART1

static uint8_t stdio_buff[80];

static ring_buffer stdio_ring_buffer;

#endif

PORTA, PORTB, PORTC what gate is??