Transitions
Transitions describe the flow of processing in a process definition. A transition is represented by an arrow between two activities. The arrows are unidirectional, and you cannot draw a transition to a previously executed activity. Control flow in a process definition must proceed sequentially beginning with the Start activity (or a process starter) and ending with the End activity.
A transition can optionally specify a condition. The condition determines if the transition is taken when an activity completes processing. After an activity completes, all transitions whose conditions are met are taken. You can have transitions from one activity to many other activities. Therefore, you can have several branches of activity processing in your diagram.
Each activity in a process definition must have a transition to it, or the activity is not executed when the process executes.
Transitions and Conditions describes transitions and conditions.