Train

The whole journey to Naples is only 4 hours (then around an hour to Sorrento) and the train stops at

Barletta

Foggia

Benevento

Caserta

Recale

Marcianise

Gricignano-Teverola

Aversa

S.Antimo-S. Arpino

Frattamaggiore-Grumo

Casoria-Afragola

on the way to Naples.

Since you have to change trains at Caserta anyway if you want to break the journey maybe that's a worthwhile place? Or Naples?

I'd probably just go straight through...

Not sure where you can find an interactive map (how exactly would that work). You can look up train times on the Trenitalia website: https://www.trenitalia.com/en.html
When you do a search and get a list of trains, click on the little i to the right of the train number, and it shows you the intermediate stops.

I would approach the problem the opposite way. Use a normal map to find somewhere you fancy going, then use Trenitalia to find if t is feasible.
There is a rail map here: http://www.bueker.net/trainspotting/map.php?file=maps/italy/italy.gif

Remember to use Italian place names. For example, the main station in Rome is called "Roma Termini". Also "Napoli Centrale".

http://www.viaggiatreno.it/viaggiatrenonew/index.jsp

You must select the "Regional traffic" tab on the right, pick a region from the drop-down list and zoom in to see all the secondary lines and the smaller stations.

You can also discover the intended departure and arrival tracks of any train.

Dario - thank you. When I tried it, some segments were blue while most were black. I couldn't figure out what this meant. Can you help?

The lines with trains running at this very moment are marked in blu; it's 1 am in Italy.

Thank you - do you always stay up this late?!

Thank you! This has helped...

do you always stay up this late?!

conjunctivitis, I can't sleep.

Actually, if you put the Trenitalia App onto an iPad, you can sort of get an idea where all the stations are; as you choose from a map when picking departure and arrival stations.
You can enlarge it to see all the smaller stations.

What is the tax code when creating a login?

The tax code is only needed by Italian residents, so they can claim expenses when travelling on business.

You don't need to register to purchase tickets on trenitalia. Turn auto-translate off, use the English version of trenitalia.com and select the "go on without log in" button inside the Authentication box

If you really want to register and receive your Trenitalia fidelity card, you can easily get an italian tax code online, it's free. You just have to fill the fields with your name, surname, place and date of birth.

What kind of seating do I want? Super economy, first class/2nd class? We are middle class, beer glass people. Can roll with the punches.

Where is the best place to find discount codes?

One more questions...I want to travel on July 24 from bari. I put in that date and it gives me solutions for July 25th. Do trains not run on the 24th?

2nd class (standard) is perfectly adequate. No need for 1st class.
2nd class is 2+2 seating, 1st class is 2+1

Lots of info about Italian trains, including photos and videos of 1st and 2nd class, here: https://www.seat61.com/Italy-trains.htm

Not sure what you mean by "discount codes". High Speed trains (Frecciarossa) and other long distance trains are cheaper the earlier you buy. When the cheap tickets are sold out you pay more. Local trains (regionalle) are the same price whenever you buy.

You probably had a late time specified. The website probably defaulted to the time you were doing your search. If you want to travel in the morning, change the time to something like 0800.

One more questions...I want to travel on July 24 from bari. I put in that date and it gives me solutions for July 25th. Do trains not run on the 24th?

You need to put in a date and a time. It lists trains from the date and time specified.
It defaults to current date and time, for people who just want the next train.

So if it is 23:00 Today (in Italy), you change the date to 24thJuly, it looks for trains after 23:00, and the first one is the following morning!
Change the date and time to what you want and it will be OK.

I did a query for 24th July and got the following trains:

Departure 08:05 Roma Termini, Arrival 12:04 Bari Centrale, Train Frecciargento 8305, from 39.90 €
Departure 14:55 Roma Termini, Arrival 18:55 Bari Centrale, Train Frecciargento 8315, from 35.90 €
Departure 16:48 Roma Termini, Arrival 21:25 Bari Centrale, Train Frecciargento 8319, from 34.80 €
Departure 18:03 Roma Termini, Arrival 21:59 Bari Centrale, Train Frecciargento 8323, from 39.90 €

😂 Thank you for your help!