Upvote:6
The website lists the different price tiers available: Saver, Value, Flexible, and Premium. If you click one of these tiers, you'll see a table showing the differences:
Some fares are non-refundable, others with fees, and others completely refundable. The actual coach or business class seats are the same. In some cases, not all these tiers may be available, as they may have sold out or not be an option for this train (this is for a faster flagship Acela Express train; here's a blog post that compares the two services):
No saver fares are available for this train, and once the value fares are gone, only the more expensive flexible fares will be left.
Seats are unassigned; first come first serve.