The Opal card is a smart card used for travel on public transport in New South Wales, Australia. It can be used on trains, buses, ferries, and light rail services. Users can load money onto the card and tap it on card readers when boarding and alighting from transport services. The Opal card offers various benefits, including discounted fares and daily caps on spending. It is available in different types, such as adult, child, and senior cards, catering to various user needs. The card can be easily topped up at numerous locations, including stations and convenience stores.