i) Atmel ATmega328P Microcontroller
ii) 6x Analog IN
iii) Power IN
iv) Power OUT
v) DC Power Jack
vi) USB(Power 5v)
vii)LED
viii)14x Digital In/Out
ix)Reset Button

Basic Brief Idea About Parts Of Arduino UNO:

ATmega328P Microcontroller: It is high performance and low power controller from Microchip.

 It is 8-bit Microcontroller  based on AVR RISC architecture.

All About ATmega328P Microcontroller:

  It has total 28 pins.One side 14 pins and another side 14 pins.

 1st pin is Reset Pin.If We use that pin,it starts to work from the beginning.

  2nd Pin is d-0 pin(Digital pin no 0). It is RX pin.RX means receiver.

  3rd pin is d-1 pin(Digital pin no 1). It is TX pin.Is helps to transfer signals.

  4th pin is d-2 pin(Digital pin no 2).

  5th pin is d-3 pin(Digital pin no 3).It uses as PWM(Pulse With Modulation).  

  6th pin is d-4 pin(Digital pin no 4).

  7th pin is VCC(+)

 8th pin is Ground Pin.

  In 9th and 10th pin there is a crystal oscillator.

  11th pin is d-5 pin.[PWM]

  12th pin is d-6 pin.[PWM]

  13th pin is d-7 pin.

  14th pin is d-8 pin.

  15th pin is d-9 pin.[PWM]

  16th pin is d-10 pin.[PWM]

  17th pin is d-11 pin.[PWM]

  18th pin is d-12 pin.

  19th pin is d-13 pin.

  20th pin is VCC.

  21th pin is Analog Referance Pin.

  22th pin is Ground.

  23th pin is A.I 0(Analog Input 0)

  24th pin is A.I 1(Analog Input 1)

  25th pin is A.I 2(Analog Input 2)

  26th pin is A.I 3(Analog Input 3)

  27th pin is A.I 4(Analog Input 4)

  28th pin is A.I 5(Analog Input 5) Pin.

NOTE: This is a brief discussion about Arduino UNO and PINS.