A NoSQL database is a type of database that has been designed for efficiently scaling as demands grow. The need for NoSQL databases arose when companies could not achieve scale with traditional database systems, also known as relational databases. NoSQL databases are designed such they can be multiplied (scaled horizontally) and the way data is stored, is designed to be retrieved very quickly, making it a good choice for certain types of workloads that are being run in the cloud. A good example of a NoSQL database is AWS DynamoDB or Azure CosmosDB.
in other words
A house that can have as many additions built on as possible.