Overview
Installing ComfyUI and installing an image-generation model are separate tasks. The application supplies the interface and execution framework, but a checkpoint supplies the model used to generate images. A fresh installation can open successfully and still fail when a prompt is queued because no checkpoint is available.
A checkpoint is therefore the foundation of every generation workflow. Different checkpoints are suited to different visual outcomes, including realistic images, anime, watercolor, and stylized character designs. The model selected in the checkpoint loader influences the style and character of the resulting image before any prompt or sampling parameter is considered.