SNOMED CT content is represented using three types of components supplemented by Reference Sets, which provide additional flexible features.
CT concepts represent clinical thoughts, ranging from abscess to zygote. Every concept has a unique numeric concept identifier. Within each hierarchy, concepts are organized from the general to the more detailed. This allows detailed clinical data to be recorded and later accessed or aggregated at a more general level.
SNOMED CT descriptions link appropriate human readable terms to concepts. A concept can have several associated descriptions, each representing a synonym that describes the same clinical concept. Each translation of SNOMED CT includes an additional set of descriptions, which link terms in another language to the same SNOMED CT concepts.
SNOMED CT relationships link concepts to other concepts whose meaning is related in some way. These relationships provide formal definitions and other properties of the concept.
Reference sets (Refsets) are a flexible standard approach used by SNOMED CT to support a variety of requirements for customization and enhancement of SNOMED CT. These include the representation of subsets, language preferences for use of particular terms and mapping from or to other code systems. Every reference set has a unique numeric concept identifier.
To learn more about SNOMED CT please see the SNOMED CT 5-Step Briefing and the NLM SNOMED CT Overview.