Rohan is a Engineering student and he recently started working on salesforce. He is trying to understand the "Batch Job". He don't know about what is the main use of "Database.Stateful". Please...

Extracted text: Rohan is a Engineering student and he recently started working on salesforce. He is trying to understand the "Batch Job". He don't know about what is the main use of "Database.Stateful". Please explain him in your own words. Apex, Salesforce