These have different sizes for the sockets and plugs.
USB-C is a newer technology that permits faster phone charging.
The iPhone socket is called Lightning. The included cable has a Lightning plug and on the other end a USB-C plug. If you buy a USB-C power adapter of 18 watts or more, you can use the included USB-C to Lightning cable to enjoy faster charging. However, you can still use the older power adapters, which come in 5, 10, or 12 watts, and use the older cords included with previous iPhones. These are a USB-A adapter, and a USB-A to Lightning cable. The only difference is that this type of cable carries less power, so it will take longer to charge the phone.