Styles define the components that make up a diagram. You can use the pre-defined styles from the provided diagram templates or you can define your own. Like paragraph styles in word processors, diagram styles define how elements of a diagram appear and behave. They consist of shape information, colors, fonts, line weight, and so on.
A diagram template is a collection of pre-defined styles that you use to build a particular type of diagram. For example, a flowchart is a type of diagram defined by a diagram template. It consists of styles for all the symbols such as Process, Terminal, and Decision, plus styles for the most commonly used text labels and connecting lines (arrows). You build a diagram by creating diagram elements of the different styles, adding text, and connecting them with lines of different styles.