I was trying to book train tickets on the GNER site from London to Stratford-Upon-Avon, and it gave me 2 options:

Stratford-Upon-Avon Station
Stratford-Upon-Avon

What's the difference?

None.

GNER's website is too stupid to distinguish between places that have multiple stations, like London, from places that have only one, like Stratford.

I would use nationalrail.co.uk, not GNER, anyways. GNER will put on the correct train, even though it's run by Chiltern, not GNER, but it's much easier to use.

Beware of their alternate suggestions that take you from Euston to Birmingham New Street, then walk to Birmingham Moor Street to continue on to Stratford. You want the no-stop trip from London Marylebone (unless you're already going to be in Euston for some reason).

My guess is it is one and the same, however, to play safe opt for the station one. Also, you might want to try the Chiltern rail site as they have direct trains from Maryebone station in London. Another service leaves from Euston with a transfer at Birgingham Moor and a change of trains on the Central line.

Sorry, we posted at the same time.

Thank you both for such a quick response. Our plan is to leave from London Marylebone to Stratford. i'll check out Nationalrail and Chiltern sites. Thanks again!!

Nationalrail gets you every company. The individual train companies, like Chiltern, are getting their data from nationalrail's site.

There is no need to book in advance for Chiltern trains, except for their E-Day tickets.
www.chilternrailways.co.uk