Deep Learning Defined
Deep learning is a way to learn functions by stacking layers of simple units (neurons) so that the whole network can approximate very complex input→output mappings. A neural network is just a composable function:
output = layer_L(...layer_2(layer_1(input))).
Why “deep”? Because there are many layers (depth). Why “learning”? Because the network’s numeric knobs (its weights and biases) are tuned to minimize a loss—a number that measures how wrong the network is on your data.
