Databases can be broadly categorized into two groups:
Relational databases: The traditional data storage architecture for storing structured data. Key value pairs are used to store information into tables consisting of columns and rows. Database queries are conducted using SQL.
Non-relational (NoSQL) databases: An alternative data storage architecture well suited to storing unstructured data. Document data stores, column-oriented databases, key-value stores and graph databases are all examples of NoSQL databases. While many of these NoSQL databases technically support SQL-compatible queries, the underlying query strategy is fundamentally different.