TLK are express running on many routes all across Poland. They are cheaper than the high-quality EIP and EIC trains and usually consist of classic older rolling stock. Also, most night trains both in Poland and to neighbouring countries are classified as TLK.
TLK trains consist of classic carriages with 1st and 2nd class seats on most routes. Almost all trains convey compartment coaches only with six seats per compartment in 1st class and eight or six seats in 2nd class. Only some carriages have air-condition, power sockets and facilities for the disabled. Most services convey bicycles.
TLK night trains usually convey former 1st class compartment coaches (which are operated as 2nd class) with six seats per compartment, couchette cars and sleeping cars. Couchettes have three or four berths per compartment, sleeping cars have one to three berths.
Reservations are compulsory; they are available free of charge at train stations in Poland. Outside Poland they cost the standard reservation fare (3 - 5,90€)
You can enter the train without a reservation, the on-board fee is 10 PLN.
If a train is fully booked you can still go on the train without a reservation but wont have a seat.