Neo4j started as a graph database and has evolved into a rich ecosystem with numerous tools, applications, and libraries.
This ecosystem allows you to integrate graph technologies with your working environment seamlessly.

What is a Graph database?

A graph database uses graph structures with nodes, edges, and properties to represent and store data.
The graph relates data items to a collection of nodes and edges, where edges represent relationships between nodes.
Graph database is designed to treat the relationships between data as important as the data itself.

Why Graph database?

A relational database uses a ledger-style structure and stores data in rows and columns.
- The relation between the two tables is mentioned using foreign key constraint.
- This becomes complex in case of an indirect relationship between lots of data because of many joins and normalization, creating data redundancy.
In such cases, where relationships between data items are more critical, graph databases become more powerful.
Graph database answers the questions you didn’t expect.
- Suppose you want to know — how many people bought a TV from a particular company, live in a particular city, and used the coupon offer in yesterday’s paper.
- If you use a relational database, this question will take much time and other resources to answer.
  - Still, with a graph database, it becomes a much simpler case with available data.

Nodes are the entities in the graph.
- They can hold any number of attributes (key/value pairs) called properties.
- Nodes can be tagged labels, representing their different roles.
- Node labels also serve to attach metadata to specific nodes.
Relationships provide directed, named, semantically-relevant connections between two node entities.
A relationship always has a type, a direction, a start node, and an end node.
- Relationships can also have properties.

Neo4j (Network Exploration and Optimization 4 Java) is a graph database management system.
- It is highly scalable, schema-free (NoSQL), and supports ACID rules.
- Neo4j follows the property graph model to store and manage its data.
Neo4j provides a powerful declarative language known as Cypher.
- Cypher is a human-friendly query language that uses ASCII-Art to represent visual graph patterns for finding or updating data in Neo4j.