Plug adapter- C or F? Or both?

Your F adapter will also fit in a C wall plug. No need to buy an additional adapter.

Thank you! Our hotel said they use type C - so it's good to know the F will still work. I appreciate your help!

The difference between the two is that Type F is grounded, where the Type C is not. But as Dutch Traveler indicated, they are interchangeable. You can get small Type C adapters easily (and cheap) at Target or any big box store. The small C adapters are a bit more universal, in that they can fit in the recesses and grounding variations you find across Europe (like type E you might find in France and Belgium, and types you find in Switzerland) Basically it never hurts to have a few C type adapters.

Thank you, Paul! This is very helpful! We will be headed to Belgium and France too and I thought I may have to buy an E, so it's good to know the C would still work!

Type C will work anywhere in Europe outside of those places that have UK sockets (although there is a trick to get them in UK sockets as well...). But they only work for appliances that do not require a ground. So they are fine for most chargers etc... Hence most tourists are fine with just a C.

It's on how a safety earth is connected that there are differences. There type F and E are most common, but appliances that require a ground in Europe come with a plug that fits in both F and E, so it is possible that your adapter which you believe to be F is in fact F/E
If you look here https://www.worldstandards.eu/electricity/plugs-and-sockets/ you will see that F and E sockets are different, but the plugs used are the same. That you can provide appliances with plugs that fit both E and F is the reason that there is no hurry moving to a common standard, as the problem is basically solved already.

The only odd ones are Denmark and Switzerland, but there C fits too.