train from Vienna to Venice

Here is a blurb from City Night Line on couchettes, continue on the link for sleeping compartments. http://www.bahn.com/citynightline/view/en/service/komfortklassen/liegewagen/uebersicht_en.shtml Basically it is the difference between a bunk room and your private room. The couchettes (either 4 bunk or 6 bunk. You can book the whole 4 person couchette by paying for the 4th bunk. The 2nd class sleeping compartment has a small vanity sink and its your own private room with 2 bunks. The first class deluxe sleeping compartment has a toilet and shower. My experience is with City Night Line operated by Deutsche Bahn. OEBB might have variations. Check seat 61 for more details on various national trains.
www.seat61.com

I think that must be an Austrian Railways Euronight service, in which case you can see photos of the different types of compartment at: http://www.seat61.com/train-from-cologne-to-vienna.htm#.UYUZ9jxwbbU