That map indeed only shows some of the main routes. It surely does not define where Eurail is valid. I never use it.

Also check country-info : this may have more detailed maps. BUT in some countries this is also very much overdone and looks like all main roads are in-where no trains run (Macedonia).

In the past, when it was all paper, one would get a brochure with better maps to give this information.

But how about a decent map of the current running Argentino ferrocarriles? is also never ever found

Is there any way to know if the trip that i want to do is included in the global pass?

TBH i still don’t understand how does this work, opposed to buying a regular ticket and knowing I’ll be able to do X trip.

Basically all trains that are operated by the participating railway companies.

What do you mean with "X trip”?

Let’s say i need to go from london to paris, so I head to the eurostar webpage, pick a train, pay for the ticket and I’m done, I know exactly at what time i have to be in the station and which train to take.

Now let’s suppose i have to do the same trip but i have the eurail global pass, now what? the day of the trip I go to the station and go inside any eurostar train that I want? anytime? how does it work?

Thanks for the other answer btw.

For some trains you will need to buy a reservation with eurail. E.g. Eurostar.

Eurail pays off the most in Central Europe (Germany, Switzerland, Austria, …) because you need no reservations (except for nighttrains) 

The map only gives an overview of main routes and destinations, and is no way comprehensive. If you'd like more specific info, we have dedicated info page on traveling by train in each country. We have also have information most high-speed, night and scenic trains. You can also find a full overview of included trains in our pass network over here. Lastly, there is a ton of information available on the community :)