The 13 different types of UML diagram each have a slightly different symbol set. Class diagrams are perhaps one of the most common UML diagrams used and class diagram symbols center around defining attributes of a class. For example, there are symbols for active classes and interfaces. A class symbol can also be divided to show a class's operations, attributes, and responsibilities. Another common UML diagram for use cases will have unique symbols for actors and use cases. SmartDraw will include all the relevant UML symbols based on the type of UML template you select.
Lines are also important symbols to denote relationships between components. Generalization and Inheritance are denoted with empty arrowheads. Composition is shown with a filled in diamond. Aggregation is shown with an empty diamond. Dependencies are marked with a dashed line with an arrow.