What is Graph
A graph is a pictorial representation of objects which are connected by some pair of links. A graph contains two elements: Nodes (vertices) and relationships (edges).
What is Graph database
A graph database is a database which is used to model the data in the form of graph. It store any kind of data using:
Nodes: Nodes are the records/data in graph databases. Data is stored as properties and properties are simple name/value pairs.
Nodes can be grouped together by applying a Label to each member. A node can have zero or more labels. Labels do not have any properties. Storing data in Neo4j is similar to add more records in other databases.
Relationships: It is used to connect nodes. It specifies how the nodes are related.
Properties: Properties are named data values.
Popular Graph Databases
Neo4j is the most popular Graph Database. Other Graph Databases are
Graph database is very useful now a day because in graph databases data exist in the form of the relationship between different objects. The relationship between the data is more valuable than the data itself.
Relational databases store highly structured data which have several records storing the same type of data so they can be used to store structured data and, they do not store the relationships between the data while graph databases store relationships and connections as first-class entities.
The data model for graph databases is simple compared to other databases and, they can be used with OLTP systems. They provide features like transactional integrity and operational availability.