A called process is a complete process that is called from another process. There is a parent-child relationship between the calling process and the called process, that is, the flow in the child process is essentially contained within the parent process.
A called process is an independent process that is called from a call activity in a parent process. Process flow goes from a call activity in the parent process to the start element in the called process. While the called process is executing, the parent process is paused. When the flow reaches an end element of the called process, processing returns to the call activity.