Raspberry Pi is a small yet powerful computer. Just like desktop computers, it runs with an operating system. There are more than one operating systems are available. Raspbian is the official operating system of Raspberry Pi. To install it, first you need to download the operating system image, then write the image to a micro SD memory card.
Raspbian with desktop and recommended software: Image with desktop and recommended software. Select this if you're planning to use your Raspberry Pi as a desktop computer, and you want some recommended software to come preinstalled. Recommended if you're beginning with Raspberry Pi.
Raspbian with desktop: Image with desktop. Select this if you're planning to connect your Raspberry Pi to a monitor and use it as a desktop computer.
Raspbian Lite: The minimal image. Select this if you're planning to access your Raspberry Pi using the terminal, and use it as a node or development board. We recommend using this version with most of our boards.
Download the one which is most appropriate for you, and then extract the archive you downloaded.
To write the operating system image you downloaded to a micro SD card, you can use a flash application. We recommend using Etcher. Go to www.balena.io/etcher/ then download and install Etcher.
Now, insert micro SD card to your computer, then open Etcher. Using the "Select image" button, open the Raspbian image you extracted from the downloaded archive. Its name should be like "2019-07-10-raspbian-buster-full.img". Then, use the "Select drive" button to choose the micro SD card you inserted. Because Etcher is going to erase everything on the micro SD card, double-check you have no files remaining on it. Finally, press "Flash!" button to write operating system files to the micro SD card.
When flashing finishes, close any opening folders (if any), and go to the next step to configure WiFi connection. Do not remove micro SD card from your computer at this step.