A subprocess is a modelled process wich is started by a so called main process.
Said main process is paused while the sub-process is unfinished. Thus it makes sense to outsurce complex but coherent tasks, wich must be finished for the process to proceed into a subprocess.

A sub process must be modelled before it can be used. You have to create a new process, which depicts the sub process.

As soon the sub process is modelled, it must be deployed. Then you have to drag&drop a “collapsed sub-process” to the place in which the sub process should start. Name it like the pool of the sub process was named. Afterwards deploy the main process.

Step 1	Step 2

Variables, Notes or documents can be interchanged between main and sub processes. For further explanation see:Inherit Variables to a sub process, Inherit documents to a sub process, Inherit notes to a sub process, Transfer documents to a main process, Transfer documents to a main process