Luggage transfer is included in your package, when not offered as optional service. This service is usually provided by the accommodation itself or a local taxi driver.
Bags should be ready at the reception or storeroom in the morning and will be delivered to the next accommodation in the afternoon.
If you are unable to do the programmed route on a given day, in some cases you might be able to arrange to ride with the luggage transport, though this option is not always available. When it is, you may have to pay a small fee locally. In some countries they have special insurance for transporting people and some vehicles might not be suitable for passengers.
When you travel by public transport you always take your luggage with you.