system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What the heck were travellers cheques? How did they work? Who accepted them, and are they still in use?

Why were they so popular in the past? I can't imagine a McDonald's in Germany accepting them, for example? Argh!
gpt
In the days before digital technology and when cash was the most important form of payment, taking money to foreign countries was really difficult. You could take a credit card, but they weren't accepted everywhere, you certainly wouldn't find an ATM that would accept them, and credit card fees were quite high anyhow.

You could just take cash with you. You could take cash in your own currency and exchange it for local currency when you were there; or you would buy some local currency before you left home and take that. But carrying large amounts of cash is dangerous: it could be stolen or simply lost, and then it's gone.

Travellers' cheques (or "travelers' checks" to use the American spelling) were basically pieces of paper issued by an agent, like American Express. In your home country, you would buy a number of these cheques, each cheque being worth a specific amount. You would sign each cheque, and then take the cheques with you.

When you were in the foreign country, and you needed some cash, you could cash one or more of your travellers' cheques, usually at a bank (you wouldn't spend it directly at McDonald's). You would have to countersign each cheque in the presence of the cashier, and possibly also show ID. You would then receive an amount of local currency equal in value to the value of the cheque, according to that day's exchange rate (minus a small commission). If you lost your cheques or had them stolen, you could have them replaced.

They're much less common now, but they still exist. Credit cards and debit cards, and now contactless payments and other technologies, have made travellers' cheques mostly unnecessary. There are also some security concerns, such as a black market in travellers' cheques falsely reported as stolen.