Jenn, I like to refer to the thing that changes the voltage as a converter, because it converts the voltage. The thing that fits our plugs to the foreign power sockets, I refer to as an adapter, because it simply adapts the plug.
Now that I have got the definitions out of the way, I hope the following explanation will make sense:
If you have dual voltage devices, then as Dax says, you would not need a converter. But it is usually only electronics, like battery chargers, and so on that are dual voltage. Devices that generate heat, like curling irons, travel kettles and hairdryers are usually only single voltage. (Not always, there are sometimes dual voltage curling irons, etc. - you would still need to check the label.)
For the converter, if you need it, it would be the same as you would use in the UK, or in Europe. But, you need to be careful to make sure that your converter is the right kind. There are two basic types. One is good for electronic devices (chargers, etc.), but can’t handle the power draw of a curling iron or hair dryer. The other type is good for the higher power draw, but will often say “not for use with electronics,” or something similar. There are some converters that are suitable for both, but I think they are sometimes more expensive than one each of the other types.
For the adaptor, it is most likely that you will need one suitable for plugging into a European type of outlet. Some of the hotels in Cuba have a plug that will accept a two-prong North-American style plug, and others will have a plug that will accept either European or the two-prong North American type. If your devices have a three-prong plug, you would need an adaptor to allow you to plug in a three-prong plug to a two-prong outlet.
One other caution: some North-American devices have a polarized two-prong plug. One prong is wider than the other, so you would need an adapter that you can plug the polarized plug into, and then plug the adapter into the wall.
I usually take two adapters. One to fit the European plug, and one to fit the North-American plug. Both of my adapters will accept the polarized plugs that I have on some of my devices.