In increasing portions of the world, and especially in Europe, most debit and credit cards have a chip on them, like this one:
However, not all cards have these chips on them, whether that's because they come from a part of the world that doesn't use them (eg a fair number of US cards), or because they're emergency replacement cards, instead there's just the magnetic strip but no chip. A bit more modern than this one though!
We've already had one question touching on this, which mentions the issues with trying to buy train tickets with a non chip (non-EMV) card in the UK.
What about if you buy the train ticket online, going through all the security there, and just need to pick up your ticket from a UK ticket machine. If you have your non-chip card and your booking reference, can you still collect your tickets from a ticket machine?