Travel and transport
Arlanda Airport
Stockholm Arlanda Airport is Sweden's largest airport, and is a juncture between Stockholm and other Swedish cities as well as the rest of the world.
Transport from Arlanda airport to Stockholm
There are a number of alternatives for travelling to and from the airport: www.swedavia.com/arlanda/to-and-from-the-airport/
Trains
There are express trains, commuter trains, and long-distance trains if you choose to travel by train to and from Arlanda.
Bus
There are Airport Coaches that go straight from Arlanda Airport to Stockholm City Center at regular intervals. (During day-time, every 15 mintues.)
Transport in Stockholm
By metro, tram, bus, ferry, or commuter train. Stockholm's local transportation network takes you almost anywhere.
Stockholm Public Transport, SL, is responsible for buses, underground trains, commuter trains, trams, and certain ferry lines in Greater Stockholm.
A single ticket is valid for 75 minutes and costs 42 SEK (26 SEK for senior citizens and children/teenagers/students up to the age of 20). It can be purchased at SL's customer service shops, through their app, or directly at the turnstiles and on buses using a credit card. It's also possible to buy 24-hour, 72-hour, 7-day, and 30-day tickets.
More information here:
www.visitstockholm.com/travel-info/public-transportation-in-stockholm/