The Pomorska Kolej Metropolitalna (Pomeranian Metropolitan Railway, abbreviated as PKM) is worth knowing about if you want to get to the airport on public transport or venture down into Kashubia. The line was only completed in 2015 and as well as opening up towns like Kartuzy as commuter towns it also connects the three cities with the airport. 

Trains run regularly between the airport’s own station and Gdańsk Głowny, although a change may be required at Gdańsk Wrzeszcz. Passengers travelling to and from Sopot may also have to change at Gdańsk Wrzeszcz. There is a direct link with Gdynia but note it leaves from the opposite platform. Tickets can be purchased from ticket offices, one of the frustratingly few ticket machines on the platform or from the conductor (+2.80zł / only a single ticket, no return tickets). You can find the timetable at rozklad-pkp.pl/en