The cards I'm asking about are sometimes called "travel cards" or "prepaid cards" or "forex cards". I don't know if there is one universally accepted name.
I have never used one because I believe they are not suited to my style of travel, but maybe I'm wrong about that.
I believe you pre-load them with amounts of money in one or several foreign currencies.
I believe that many banks in many countries provide them but that places other thanks banks sometimes also provide them.
I cannot find the Wikipedia page or even decide what is the most usual term. But here is the link for the card of this type that my bank here in Australia provides, as one example for those who need more info about what I'm talking about. And here is a Quora question about them where I learned they are also called "forex cards", which I have used as a new tag since "travel card" is obviously ambiguous.
My actual question about them is:
When are these cards not suitable for travellers? Do they have any down sides?