A Sound is a chain of 1 to 5 layers, each with their own chain of FX.
A layer is an engine and possible FX.
So 5 of such layers can create a multitimbral sound, all stacked up with their own colume or with split-points.
One can save this stack of layers with all its information of each layer into a Sound file, which can be recalled and shared later, provided the plugins and FX are available on the target zynthbox machine.
For sharing and finding sounds, please go here: