A Fork Node splits a flow into multiple concurrent flows, while a Join Node synchronizes them.

1. A Fork Node can have exactly one incoming Activity Edge (or Transition), though it may have multiple outgoing Activity Edges (or Transitions).
2. A Join Node can have exactly one outgoing Activity Edge (or Transition) but may have multiple incoming Activity Edges (or Transitions).

The Fork and Join are represented by the same symbol. Although, you can set the Use different Fork/Join and Decision/Merge notations project option to draw different notations for the Fork and Join. This option is set to true by default.

An example shows the different Fork and Join notations