Both Apple Pay and Google Wallet are Mobile Payment services that use your smartphone to pay for things. Both of these payment methods depend on NFC hardware, the phone communicates wirelessly with the contactless payment terminal.
Google Wallet, which made its debut in 2011 was replaced in 2018 with Google Pay. Apple Pay was introduced in 2014
Both are similar to what Visa payWave and MasterCard PayPass use for contactless payments. This involves tapping or waving over a card over a reader instead of swiping or inserting the card.
For starters, they both work in most NFC enabled Merchant terminal. Apple made a big deal about partnering with certain stores like Whole Foods and McDonald's when it launched Apple Pay, but in reality any location that has an NFC-enabled point-of-sale system should work with Apple Pay or Google Wallet, of course, has worked with such systems for a little over three years. There are some exceptions.
Both Apple Pay and Google Wallet require Multi-Factor Authentication and a NFC enabled phone.
Apple Pay Take your iPhone out of your pocket, rest a finger over the Touch ID sensor (without pressing down), and hold it over a contactless payment terminal.
The iPhone uses Touch ID to authenticate your fingerprint and immediately processes the payment.
Google Wallet Take your phone out of your pocket and hold it over the reader. You may then have to enter your Google Wallet PIN (if enabled), which should different from your phone-unlock PIN for security reasons.
Google Wallet works on a large range of Android phones, as many Android phones sold in the past few years have had NFC hardware in them. Google Wallet also works on the iPhone 6 and iPhone 6 Plus, and uses Touch ID (instead of a pin).
Apple Pay and Google Wallet, once set up, should work at any NFC enabled Merchant terminal.
Apple Pay is US-only at this time. (2015-02-11) where Google Wallet is international (as of 2015-01-29).