This document discusses the layers of convolutional neural networks (CNNs). It provides an overview of common CNN layers including convolutional layers, max pooling layers, padding, rectified linear unit (ReLU) nonlinearity, and fully connected layers. Convolutional layers extract features from input images using small filter matrices in a sliding window approach. Max pooling layers reduce the dimensionality of feature maps. Padding handles edge effects when filters are smaller than inputs. ReLU introduces nonlinearity. Fully connected layers flatten feature maps into vectors for classification. The document reviews the functions of these key CNN layers.