NoSQL is a collection of data items represented in a key-value store, document store, wide column store, or a graph database. Data is denormalized, and joins are generally done in the application code. Most NoSQL stores lack true ACID transactions and favor eventual consistency.
BASE is often used to describe the properties of NoSQL databases. In comparison with the CAP Theorem, BASE chooses availability over consistency.
Basically available - the system guarantees availability. Soft state - the state of the system may change over time, even without input. Eventual consistency - the system will become consistent over a period of time, given that the system doesn’t receive input during that period.