The Big Picture: What TensorFlow Does

• Represents computations as a graph of ops connected by tensors.
• Uses automatic differentiation to compute gradients of a loss with respect to variables.
• Executes efficiently on different devices (CPU/GPU/TPU), scheduling and batching work.
• Provides optimizers (e.g., SGD, Adam) to update model parameters.

The magic: You describe the forward pass (how outputs are computed). TensorFlow builds enough metadata to compute the backward pass (gradients) automatically.