On all forms of public transport and with all operators nationwide, the ticket used is called an ov-chipkaart (public transport smart card). You can either get a personalised card or a general one which you deposit money on. Machines to top up can be found at train stations, supermarkets, kiosks and newsgates. On buses and trams you can also buy a disposable ov-chipkaart from the driver, but they are relatively expensive. You can't pay with cash on Dutch public transport. (not available due to corona)
Remember, at the start of your journey, to always check-in by holding your card against one of the card readers. For train journeys you cannot check-in if the balance on your card is below €20. At the end of your journey, or if you change to another mode of transport, you check-out. On buses and trams - you must check-out, and check back in -even when just changing to a different line. If you forget to check out, €4 will be deducted from yout card when travelling by bus, tram or metro. For more information about the ov-chipkaart, check the website www.ov-chipkaart.nl/en