What is Open weights
A model whose trained files are published for anyone to download and run on their own hardware.
In plain terms
The weights are the numbers a model learned during training, and they are what makes it work. A lab that publishes them lets anyone run the model on their own computers, adjust it, and use it without sending data to an outside company. Llama is the best-known example. Labs that keep their weights private sell access through an API instead.
What it tells you about a developer
Open-weight work means the developer has served a model themselves: choosing hardware, watching speed and cost, and keeping it running. Teams in health, finance, and defense reach for open weights because their data cannot leave their network.