Relational databases have been an essential component of technology for many years. It has been, and in some cases, still is, the foundation of both large and small organizations. However, a few flaws in relational databases gave rise to NoSQL databases. NoSQL is not a particularly new technology, but it is one that is rapidly expanding. The structured query language is also known as NoSQL. Today, a variety of NoSQL databases are accessible depending on the user's needs. This review combines numerous comparisons of these databases based on various attributes. A few terms relating to NoSQL databases are also clarified and brought to light. Additionally, a detailed comparison of the two most popular NoSQL databases is evaluated.NoSQL is a component of a very narrow ecosystem with fewer applications than relational databases. Relational databases are fairly straightforward, which makes them easy to use, but the non-uniformity of the expanding data causes an issue with them. Organizations manage millions of pieces of data, which makes using a relational database challenging. Additionally, the IoT is right outside our door, and NoSQL is better for IoT applications. NoSQL was developed to address this non-uniformity and the rapidly expanding data sets. NoSQL is mostly utilized in distributed, cloud, and IoT systems. NoSQL databases eschew rigid schemas and prioritize availability, scalability, and fault tolerance as key properties.