These are 3D blueprints. They contain the shape but no instructions on how to build it.
Sites like allow you to generate custom G-Code files for things like temperature towers and retraction tests. These are downloaded as ready-to-print files to help you fine-tune your hardware. The Risks of Downloading G-Code
Almost every printer (Creality, Prusa, Bambu Lab) comes with a set of "Sample G-Code" files. These are optimized specifically for your machine to prove it works. If you’ve lost your SD card, visit the "Support" or "Downloads" section of your printer manufacturer's site. 2. Printables (by Prusa)
