NoSQL is a movement that promotes software systems where data persistence is characterized by not using the relational model, usually used by traditional databases (RDBMS). The expression NoSQL refers to the SQL language, which is the most common language of querying data in relational databases, here taken as a symbol of the entire relational paradigm.
These data archives most often do not require a fixed schema (schemaless), often avoid junction operations (joins) and aim to scale horizontally. Academics and articles refer to these databases as structured storage (structured storage).
source wikipedia