An increasingly popular type of database. In contrast to relational databases, which rigidly require information to be stored in pre-defined tables, document-oriented databases are more free-flowing and flexible. This is important when you don’t know what is going to be thrown at you. Document-oriented databases retrieve information more quickly but store it less efficiently. The same document-oriented database might let you store the information for an article (headline, byline, data, content, miscellaneous) or for a photo (file, photographer, date, cutline). MongoDB is a popular open source document-oriented database.