What is an image? Why do I want one anyway?

Traditionally, all Linux installs were carried out in regular computers (laptops, desktops, servers, etc.) were done by each distribution’s installation programs (for us, that’s Debian Installer, also known as d-i). But for platforms such as the Raspberry Pi, some of us don’t think it’s the right tool. Among some reasons:

This class of computers is usually used without access to our expected typical interfaces (keyboard and screen), or is done in a no-network scenario.
The typical boot media (a SD or micro-SD card) is slower and less reliable than magnetic or solid-state hard drives. Performing a regular install to get a base system ready is… a lot of wait, and not particularly fun!
Raspberry Pi computers require a non-free firmware to boot. While it is possible to have it built into a d-i image and into the destination image, it’s nontrivial for newer users.
The Raspberry Pi traditional usage has been always from preinstalled images. There is less pushback if we do the same!

Of course, not everything is perfect. In case you download the images from here, you will be trusting images prepared by just one guy (who happens, yes, to be a Debian Developer). The distributed trust among various teams, and the verification done independently by thousands of users throughout the world, you can put in an official Debian release are diminished if you get your image from here. Much even more so if you download a one of the daily auto-built images and not one of the tested images!