ABSTRACT Since the past decade, relational database management systems have been the choice of many developers and system administrators for a variety of applications. In spite of the lack of flexibility, the powerful nature of many RDBMS allowed complex database set-ups to be created, queried and used. However, the NoSQL database eliminated the use of the standardized SQL a few years ago. Similarly, others picked up and continued to grow this thought, by referring to various other non-relational databases as NoSQL databases. NoSQL databases try to offer certain functionality that more traditional relational database management systems do not, like, holding simple key-value pairs for shorter lengths of time for caching purposes, or keeping unstructured data that could not be easily dealt with using relational databases and the structured query language (SQL). In this article, we discuss various models of NoSQL database management systems and explain their purposes and functionality and implementation criterion for all.