**Databases that aren’t just tables. There are several varieties. **
Non-relational databases are databases that aren’t simple tables of consistent rows and columns like you’d find in Relational Databases. Some domains lend themselves to relational schemas very well, others not so much. For those cases where non-relational data isn’t well suited, some type of non-relational database is probably a better fit. Any given problem may be suited best by any of the various Types of Non-relational Databases