Classification is about categorizing objects into groups. A type of classification is where multiple classes are predicted. In neural networks, neural units are organized into layers. In the first layer, the input is processed and an output is produced. This output is then sent through the remaining layers to produce the final output. The same input is processed through the layer to produce different outputs. This can be represented with a multi-layer perceptron. The type of neural network used for classification depends on the data set, but neural networks have been used for classification problems.