Hi Deepak,
A big object stores and manages massive amounts of data on the Salesforce platform. You can archive data from other objects or bring massive datasets from outside systems into a big object to get a full view of your customers. Clients and external systems use a standard set of APIs to access big object data. A big object provides consistent performance, whether you have 1 million records, 100 million, or even 1 billion. This scale gives a big object its power and defines its features.