Which trains are included in the Pass?
You can use your Pass to travel on the national railways and some private railways in the countries where your Pass is valid. In some cases, these train networks reach airports as well. Check the full list here. The Pass even includes certain buses and ferries to make sure everyhting is within reach.
Some popular trains like the Eurostar, Thalys, TGV, and AVE are included in the Interrail Pass, but require that you purchase a seat reservation.