Here is a basic guide to trains, buses and trams in the Netherlands.
The Netherlands has excellent public transport links, and the swipecard payment system OV-chipkaart is the official transport payment system for the metro, bus and tram throughout the Netherlands.
The Nederlandse Spoorwegen (www.ns.nl) is the national train company. Paper train tickets were abolished mid-2014, and infrequent train travellers can buy a single-use chipkaart at 1 EUR extra per trip. The single-use chipcard is a paper ticket with that contains a chip inside. If you are not planning on travelling a great deal, the single-use chipcard is the best option. This paper chipcard can be purchased from an NS ticket machine or a Tickets & Service desk and is valid for all train operators. You do not have to add any credit to this card. When you purchase a single-use chipcard you always pay the full fare, which means you do not get any travel discounts. There is a € 1 supplement on the four most commonly used products (single journey, return ticket, day travel cards and the AnaarBeter ticket) to cover the additional costs of the card.
For the bus and tram there is also the possibility to buy a single-use card. However, that is much more expensive than buying an anonymous OV-chipkaart from an NS ticket machine or a Tickets & Service desk. The OV-chipkaart is the public transport smartcard that is used as a ticket for all public transport in the Netherlands. The same card allows you to travel on the train, tram, bus and metro. You use this card to check in for each mode of transport as you depart and to check out again when you arrive. Your pass can be loaded from one of the OV-chipkaart machines strategically placed at train and metro stations.
If you are planning to travel by bus and train, which is necessary to reach Leiden University, we advise you to buy an anonymous OV-chipkaart from an NS ticket machine or Tickets & Service desk. Before using this card, you have to load your card from one of the OV-chipkaart machines.