Automatic lookup refers to the ability of Chinese Toolbox to display the definition of a character or word by just selecting it. Unlike most other Chinese readers, pointing at a character and clicking on it with the mouse is not the only way to select and lookup the meaning and pronunciation of a character. In fact, the preferred method of selecting in Chinese Toolbox is via the keyboard. When you press the left or right direction keys in the Reader (or click on a character), the definitions for the selected character/word appear automatically in the dictionary windows. See the tutorial, Reading in Chinese Toolbox, for examples of how to use Chinese Toolbox to read Chinese text.