Exactly what it say's on the tin. You book a cruise & arrange your own flights, transfers, hotels & transport. Some of us prefer to do this for various reasons.
It means that all travel arrangements and costs involved in getting to the ship are not included in the quoted cost (and the same applies once you get off at the end of the cruise). So it is up to you to find appropriate flights and transport from the airport to the ship.
You should bear in mind that if the flight is delayed for any reason, and the ship sails without you, then it is for you to sort out the problem of getting to the next port, the cruise line will not help you.
It means what it says on the tin...cost of cruise only. It excludes the cost of getting to the departure point i.e flights etc. Where flights are included in the price it is normally described as a fly cruise.