A trained checkpoint is a finetuned model.
A full finetuned model is a model trained using a finetuning script, leveraging Kohya, OneTrainer, AI-Toolkit, or SimpleTrainer, on a finetuning dataset
A merged model is a base model, a finetuned model, or a merged model, that is:
merged with one or more checkpoints
merged with one or more lora's
merged with one or more models and one or more lora's