From Distillery.com, a high-level overview of convolutional networks:
You should already understand — at least figuratively — the structure of the simplest ANN. Accordingly, by way of background material, let’s suffice with talking only about traditional neural networks (such as perceptron-type networks), which include only neurons and connections. To help you understand the concept, I’ll explain that a traditional neural network looks like a black box with one input and one output. It can be taught to reproduce the results of a certain function.