At the moment, there are no passengers trains running on the territory of Afghanistan, although there are some cargo lines.
The famous Khyber railway pass in Pakistan, which runs up to the border with Afghanistan through the Khyber pass, has had a rocky history and is currently not in use once more, as heavy floods have washed away part of the tracks and repairs are likely to take a long time.
If you are interested in the subject of Afghani railroads, have a look at Andrew Grantham’s website, the number one resource on past, present and future of railways in Afghanistan.