What is a Neural Network?

Every large language model — ChatGPT, Claude, Gemini, Llama — is built on neural networks. Before you can build an LLM, you need to understand what a neural network actually is, not as a metaphor, but as a mathematical function.

A neural network is a function that takes numbers as input, transforms them through a series of operations, and produces numbers as output. That's it. The magic isn't in the structure — it's in how the network learns which transformations to apply.