Open-weight models allow anyone to download the numerical values, called weights, for each of the billions of parameters stored in their machine minds. That raw information allows anyone to run a model on specialized hardware and to build on top of the model, altering its weights with additional data in a process called fine-tuning. In the industry, some also refer to “open-source” models, which provide a higher level of transparency, offering users full access to weights, training code and other data.