NOSQL databases can be categorized into 4 types: key-value stores, column family/big table clones, document databases, and graph databases. Key-value stores store data as key-value pairs and allow retrieval by key, column family databases organize data by rows and columns with variable schemas, document databases store data as documents with key-value attribute pairs, and graph databases store data as nodes and relationships. The document discusses the characteristics of each type and examples like MongoDB, Cassandra, and Neo4j.