Training Systems.

The word "mask" means at least four unrelated things in deep learning — what a token can see, what counts toward the loss, what is hidden to create a task, and what is randomly dropped. One field guide to all of them, with why each exists and what breaks without it.

You don't need a massive tech budget or a cluster of high-end GPUs to train your own AI. LoRA allows developers to fine-tune giant models right on a standard laptop. Here is the zero-jargon, first-principles explanation of the clever shortcut that leveled the playing field.