The Octopus is most widely used on the various means of transport, as most of the transport service providers accept it. These include the Mass Transit Railway (MTR), Citybus Limited and Star Ferry etc. For example, after getting on the bus, you just pass your card across the Octopus Processor so that it can read it and it will deduct your bus fare from the value on your card.

The Airport Express Travel Pass is a special Sold Octopus, which is very suitable for tourists. The Airport Express Travel Pass has two different values – one for HK$220 which offers one Airport Express trip and three days unlimited trips on the Subway Island Line, Tsuen Wan Line, Kwun Tong Line, Tseung Kwan O Line, Tung Chung Line and Disneyland Resort Line. It is sold in all Airport Express stations and the stations on the lines listed above. The other costs HK$300, and allows two Airport Express one-way trips and three days' unlimited trips on the lines mentioned. It is sold in the Customer Service Centre in every Airport Express station and MTR Kowloon Tong, Mong Kok, Tsim Sha Tsui, Wan Chai and Causeway Bay stations.

You can find more information baout it on this web page.