An offer is the price combined with certain conditions. Each room/unit has one or more offers. "Offer 1" is your standard offer to the guest which is always displayed.
You have the option to sell a room at up to four with different prices eg. packages, promotions or discounted conditional rates. Each offer can have its own "Booking Type".
If you copy a room all settings will be automatically applied to the copy. If you want to link prices between different rooms remove the prices before you copy the rooms.