Arduino IDE

IDE is a software that integrates a bunch of tools

A text editor, using which the programmer can enter the C++ program.
A compiler, which translates the C++ program into an executable file. The executable file contains a machine language program (binary) composed of a sequence of 1's and 0's. These 1's and 0's form the instructions which the Arduino board should execute.
A programmer, which uploads the machine language program to the Arduino board.

Download from https://www.arduino.cc/en/Main/Software (download the .exe version for Windows)
Online version available (but the local version is recommended).
Installation is straight forward.
Remember to allow the installation of the driver for Windows.
Note for Ubuntu Linux users : The arduino version in the apt repositories is extremely old. So DO NOT do sudo apt install arduino. Instead, install it using snap - sudo snap install arduino.

Your computer communicates to the Arduino via a serial port through a USB-Serial adapter.
Check to make sure that the drivers are properly installed.
Usually, Arduino Uno will appear next to the correct COM port.
The COM port could be different when you plug Arduino into a different USB port, or when you plug in a different Arduino board.
If you are unsure, go to device manager (in Windows, Run > type devmgmt.msc and press enter). You can then unplug the Arduino board and see which COM port disappears under the 'Ports' category.

Next, double-check that the proper board (Arduino Uno unless you are selecting another board) is selected under the Tools-->Board menu

Note : Arduino IDE supports a large number of boards, including ESP8266 / ESP32 and ARM boards. We just need to add support for those boards.