difference between open quantity and delivery quantity

Hi all,

Please anybody explain me the difference between open quantity and delivery quantity My question is both are same in the value or different I need to report these 2 fields based on date.

open quantity is available in table vbbe

delivery quantity available in table lips.

for open quantity i have one select statement.

for delivery quantity i have another select statement.

i want to club these 2 fields into a single report.

please clarify my doubt.

regards

chandu