By default most iPhones and iPads ship with Apple’s tiny 5-watt power adapters - they work but not quickly. However, the iPhone 8 and later all models of the iPad Pro, the most recent iPad Air, and iPad mini models support fast charging when connected to higher wattage power adapters.
Apple has bundled with iOS devices or sold 10-watt, 12-watt ($19) and 18-watt ($29, USB-C) power adapters and the company has also produced 29-watt, 30-watt ($49), 61-watt ($69) and 87-watt ($79) USB-C power adapters for Mac laptops. Plug your compatible iPhone or iPad into one of these chargers with an appropriate cable (for a USB-C charger you’ll need a USB-C to Lightning Cable $19) and it will charge significantly more quickly.
Look for a wattage rating on the adapter itself or multiply the output volts and amps together to get watts.