Train travel in Spain

Well, Eurail is a company that sells marked up tickets.
Every European country has their own rail system, which intersect with other countries systems. See:
https://www.seat61.com/european-train-travel.htm

Spain trains are fine, and vary. What info are you looking for?

Spain’s train system is https://www.renfe.com/es/en

We traveled mostly by train in 2017, and their trains were all fine. Also, when we took an occasional bus between cities, they were all modern with comfortable seats.

try here - 'A beginner's guide to train travel in Spain'
https://www.seat61.com/train-travel-in-spain.htm

I love train travel in Spain. You need a reservation, and must show your seat assigment/ticket with your passport to get to the platform to board the train. Sounds complated, however getting on the wrong train wont be an option. Cheap too.

There are many train companies in Spain, all public. RENFE, both long and short distance, operates on wide gauge routes and it is the largest company. Then some regions operate their own company, as well as RENFE: Euskotren in the Basque Country, Ferrocarrils de la Generalitat-Rodalies in Catalonia, FEVE is narrow gauge in northern Spain (through beautiful mountains and valleys) and belongs to RENFE...well, easy to see as trains links many towns and it´s a widely used means of transport. Modern, fast, efficient, clean and cheap, one of the best railroad systems in the world. And of course the rapidly expanding high speed train, public, that links major cities like Seville, Barcelona, Zaragoza, Valladolid, Madrid,..., the largest high speed net after China.d

True. But as you rightly say, AVLO belongs to RENFE, which is a public company in Spain and OUIGO to the SNCF, publicly owned in France, there´s a thin line here between "public" and "private". And both are focused on high speed operations only. No private companies operate on the "standard" train sector in Spain...yet.