NOOBS is the built-in operating system installer for Raspberry Pi. But if you already know which operating system you want to use, there's a quicker way to get your Pi up and running.

Boot your Raspberry Pi and you will be presented with a menu offering many different operating systems for installation. Tick the box next to Raspbian and then click Install and wait.

All you need to install any version of Raspberry Pi OS is the Imager tool, an SD card and reader, and around ten minutes.