The three key elements of SNOMED CT are concepts, descriptors, and relationships. This is a pretty complex CT system, so a more in-depth answer would be better for this answer. Unfortunately, most of the information available on the web is too in-depth for a beginner to understand. (I am a beginner at this, so I apologize if I don’t quite understand what is going on.) Despite that, I will attempt to make this easier for people to understand.
Concepts are important because they can be organized. There are many ways to organize even five concepts. Relationships basically connect concepts to each other, like how a relationship describes how two people know each other. Finally, descriptors will take terms that humans use and make them compatible with a variety of concepts.