Neo4j is an open source and the world's leading graph database management system and it is designed for optimizing fast management, storage, and traversal of nodes and relationships.
Neo4j is a highly scalable, native graph database built to leverage data and their relation and it delivers constant real-time performance, which enables enterprises to build applications to meet today’s evolving data challenges.
Having nodes with their relationships stored together in the database opens a number of use cases, without having to recalculate the relationships (or joins) for every single query, opens up a whole series of new use cases that would be very hard or impossible to implement with relational databases.
Although mathematical graph theories have been around for centuries, it took until recently for graph databases to become popular. Increased access to cheap and powerful computing resources and the development of mainly graph database market leader Neo4j have created a huge increase in demand for graph databases