Uniquely identifies one DICOM Instance. Every DICOM Instance has a UID.
A pair of an IOD and DIMSE Service that together defines a capability of a DICOM AE. At association phase, AE’s exchange SOP Class UID’s and agree on their capabilities.
A combination of a SOP Class and Transfer Syntax that is agreed upon between two applications during the association negotiation phase. The transfer syntax is used to serialize the commands and data objects of the service throughout the association.