Preset metadata is all data which describes a preset, but does not contain the preset data itself.
Metadata consists of:
Audio Preview Note
In terms of the NKS format, the plugin is usually not aware of the metadata and is only used for Maschine/Komplete Kontrol to organize presets.
A preset parser is a module which knows how to extract preset information for a specific plugin, and converts the presets into a generic format which can then be used to load the data into the plugin, or to generate an NKS file.
A type defines the category of a preset. Each type can have a main type and a sub-type. For example, the main type could be "Bass", and the sub-type could be "Acoustic", resulting in a complete type of "Bass > Acoustic".
A characteristic defines how the preset sounds. Typical characteristics are "Arpeggiated", "Soft", "Hard" etc.