Azure Cosmos DB supports Gremlin as a graph database model. If you are not familiar with graph databases, you may think about them as a structure composed of vertices and edges. They can very easily show you relations between different elements of a graph as you can quickly traverse the connections and see that element A knows something about element B indirectly, thanks to element C. To be more specific, Cosmos DB supports a more specific model of a graph database known as a property graph. The following is an example query for Gremlin:
:> g.V('thomas.1').out('knows').out('uses').out('runsos').group().by('name').by(count())
The preceding example is taken from the documentation and literally answers the question: What operating systems ...
