I have come across people talk about "backup Generation" example....we keep 5 
generation of backups or 4 generations of backup. I am not sure I understand 
this term , I think it came from main frame ...? We have retention period set 
to 30 days. and do daily incremental and weekly backup on Windows systems and 
sql db. IS that mean our one generation is all the backups taken for 30 days or 
one generation is daily backup ?

Appreciate any education on it.