Apple, representative of large multinational electronic giants, realized that it was cheaper (and likely more economically viable to have citizens across the world with iPads, iPhones, and other Apple devices) to sell devices and chargers to many, many people. With such a large market base, irritating customers with proprietary charges seemed counterintuitive.
So, most Apple devices use a USB A device to plug into the wall thingy, which itself plugs into the wall. Because different countries use different plug arrangements, an adapter is used so a Spaniard with an iPhone XS can use the same wires an stuff as a Brooklynite with the same device. In other words, the iPhone wires and adapter (providing you have the plug adaptor--$15 or less from RS) work for both you and Jose from Zaragosa.
If you read the minimal information from Apple, it will tell you this. Finding the information from Apple may be difficult, however.
In the olden days, it was necessary to use transformers to "step down" the voltage from 240 volts 50 cycles to a safer 110 volts 50 cycles. Otherwise, the device would get hot and might burn. That was bad. I haven't traveled with a transformer for more than 40 years. The simple adaptor, coupled with the device's own internal electronics (read the tag near the plug or use your magnifying glass to confirm that your other devices (hair dryers, curlers, water heaters, etc (think heat)) are dual voltage. If so, you only need the plug adapter.
The ApplePhone is an outlier, requiring the weird circular charging surface. Go with the flow, because the other end of the weird circle is the USB hub, which plugs into the wall adapter, which plugs into the plug adapter.
Enjoy your trip. If you have doubts about your hair crimper, buy one on the economy and throw/give it away when you leave.
Edited to add that I just checked my iPhone plug (the wall adaptor) and it says in really tiny letters that it is okay for 100 to 240 volts, 50 to 60 cycles, The output is DC current, in the range of .15 amperes. So, it is okay to plug it into a 240 receptacle if you have the wall adapter and the plug adapter. Case closed.
As far as phones and iPads go, use your current wall adaptors with plug adaptors and sleep easy.