Cypher is Neo4j's graph query language that uses ASCII art to draw out desired graph patterns in code. It allows users to specify relationships between nodes and data, such as "node-relationship-node" patterns, with the use of hyphens and direction indicators like "greater than" signs. Cypher enables querying complex hierarchical structures like tree-like structures, and is particularly useful for modeling real-world relationships between entities. The language supports various query types, including finding units that can be built at a building, calculating average unit cost, determining unlocked buildings and units with additional requirements, and traversing multiple levels of relationships to find dependencies. By utilizing Cypher's functions such as "shortestPath" and "UNWIND", users can efficiently analyze and visualize their data in Neo4j.