Features

Features are properties or characteristics of the raw input data. For example: number of words and number of unique words are features of a text article. Or, in the case of image data, applying a filtering operation generates a corresponding feature of the image. Features are sometimes given, sometimes computed via fixed methods (e.g. a convolution with a fixed kernel), and sometimes computed by the model itself -- e.g. the feature maps in a convolutional neural network.
Related concepts:
Feature Maps