A checkpoint loader selects a compatible image model from your model folder.
A checkpoint preserves a model's state at a particular point. Training checkpoints can also store information needed to resume training. For inference, you need the weights and configuration expected by the runtime, not a particular file extension by itself.
ComfyUI loader nodes select compatible files. Some model families need separate text encoders, a VAE or other components rather than one self-contained download. ComfyUI documents model files and loaders.
Keep the source, exact filename and model family with your notes. Replacing a file because the names look similar can create architecture mismatches. Check the official example's required components before troubleshooting the prompt. A workflow JSON normally records choices and connections; it does not bundle the large model files needed to execute them.
Sources
Primary references checked 11 October 2026. This explanation is not a benchmark of a particular model or computer.