Node symbols are the shapes that define the appearance of a node. The symbol is only one property of a node style along with color, font, size, and so on, but it is obviously the most visible. Built-in node styles have pre-defined node symbols based on the diagram type. However, you have full control to change them as you see fit.

The node symbol gallery contains hundreds of different shapes sorted by functional category. You can add any symbol to a diagram directly from the gallery, or you can use a pre-defined node style from a template (shown on the left side of the workspace).