A column-oriented database is a type of database management system that stores data in columns rather than rows. This structure allows for efficient data retrieval, especially for analytical queries that often access specific columns rather than entire rows. By organizing data this way, it can significantly reduce the amount of data read from disk, improving performance for certain types of operations. These databases are particularly useful in scenarios involving large datasets and complex queries, such as in data warehousing and business intelligence applications. Popular examples of column-oriented databases include Apache Cassandra and Google Bigtable, which are designed to handle high volumes of data efficiently.