Difference between Manual or Flat-file or Database?

well all three are more or less the same. eg. register or record books. contain simple tables prone to inconsistency, redundancy.

rdbms(Relational dbms) contains table with relations.

eg all the employees of the accounts dept. are part of the employees table of the entire organisation. hence, any changes to either should be reflected in both the tables.

this reduces redundancy, inconsistency