the serial port of the arduino is the most common way of communicating with an external device. most arduino sketches will use a serial port to communicate with the computer. but it is not necessary that they have to do so. you can also connect to the arduino via a usb connection or a network.
how do you actually open the serial monitor? the arduino software has a serial port that you can use to communicate with the arduino. this serial port is not usually visible on a desktop machine, so we need to install a serial port driver on your computer.
after opening the serial monitor, you can use the serial port for communication with your arduino. for example, you can send commands to the arduino by typing things into the serial monitor, and then pressing the enter key. the arduino will receive the serial data as text. the serial monitor should open in the arduino ide when you first connect the arduino to the computer. you can see the serial port in the arduino software.
although the arduino is a small device, it has a lot of capabilities. the arduino ide is basically a development environment for the arduino. you can install the arduino software onto your computer and then open the arduino ide. this is the software that is used to program the arduino.
the arduino has two different processors - the arduino due and the arduino uno. the arduino due has been designed to have a lot more processing power than the uno. if you look at the specifications of the due, you will see that the due has at least twice the processing power of the uno.
with the arduino ide, you can select what board you wish to use when you upload a sketch. you can choose to upload to the arduino due or the uno. you can also select to upload to the atmega 328p or atmega 328p-pu.