The start-process and end-process activities provide markers for the beginning and end of a process. They are anchor points to which other activities can be attached using transitions thus creating a series of steps from the start to the end of the process. In a valid process definition traversing all the transitions between activities starting from the start-process activity should lead to end-process activity (note that in a running process instance not all paths will necessarily be traversed, for example if a split (see Split/Join) is encountered only some of the paths may actually be followed depending on the evaluation of transition conditions). As such the simplest (and incidentally the most useless) process definition is one that contains only these two activities and a transition from the start-process to the end-process activity.
Every process definition must have exactly one start-process and exactly one end-process activity. When defining a process using the Process Definition Tool these two activities are created automatically on process creation and are not required to be (in fact cannot be) explicitly created by the user.
The start-process and end-process activities form the outermost block of a validly block structured process definition as required by Cúram workflow.