Well, you get to go 1st class — more comfortable, more roomy and less crowded, but IMO not usually worth the money.  If you’re 26 or over the only eurail pass  available (you can buy 2nd class passes for some individual countries) is an adult, 1st class pass.  A saver pass is a specially priced pass for 2 to 5 people travelling together.  The price listed is per person and represents about a 15% savings over the regular price.  It’s OK for a couple, but not a good deal if you’re likely to want to split up and go different directions at some point during your trip, or if you’re not arriving in Europe at the same time and place.