I thought ML models were tiny, small enough to run on mobile devices.
Training usually uses large amounts of data to get your system to recognize a pattern. It generally uses huge memory and compute and generates a model.
Inference will use that generated model to recognize the pattern in new data. It uses significantly fewer resources and can run either very fast or on a smaller system.
I believe the speed of inference may be affected by the resources available during training, where more speed/memory for training can produce better models.