If AutoCommit is off, then any update or insert operation
perforned on database will not be reflected just after the 
query is executed.Though the operation has been 
successfully completed.
 We will have to commit the transaction manually, to view 
the incurred changes.
  This also keeps user on the safer side, if some 
undesirable row has been inserted,updated or deleted in the 
database then it can be rollback.

While if the AutoCommit is on any update,insert or delete 
are at once reflected onto the database.