A system is a container which can hold one or more endpoints. Systems come in two different flavors - predefined systems which you can add onto the working canvas via the Wizard, and blank systems which are fully configurable however you as the user must configure that system manually (add endpoints, define data layouts, define mapping).
Predefined Systems (Wizard)
Predefined systems are ready-made platform connectors which contain one or more endpoints ready to be connected. All endpoints come with predefined data layouts. As the end user, you can simply create a link between two endpoints, create a mapping template or import one of the pre-existing templates, and enable and test your sync.
Predefined systems are made by the DSYNC engineering team internally. These connectors are fully tested and supported.
Blank Systems (Manual)
Blank system is essentially a wrapper which can become any system you like. In general, a manually created system would contain few API or FTP endpoints. You can add any number of these endpoints to the system from within the DSYNC application. Each endpoint can then have its own data layout and can be connected to any other system/endpoint you may have on your working canvas.