Cisco IOS upgrade vs update

[OMAR MASRI]

Hello

Cisco states the following in one of it's FAQs:
"Cisco may provide new versions of software containing fixes and updates (but not upgrades) to customers without charge in certain instances"

Does this apply to Cisco IOS? If so, what is the difference between an update and an upgrade? Is moving from eg 15.5 to 15.6 an upgrade whereas from 15.5(1) to 15.(5)2 an update?

Thanks

[OMAR MASRI]

Or is an upgrade for a feature only - eg. LAN Base to IP Base?

[williamehmke1]

Did you ever find the answer to your question as I am wondering the same thing