If you live in a country where tap to pay with your credit card is normal, and you own an iPhone, this is for you.
If you're a member of a major bank or credit card company, id be confident that you'll be able to setup Apple Pay on your device. If you'd like to ensure you have a compatible card, Apple has a comprehensive list of participating banks sorted by country.
The short answer here is yes. Especially if you're someone who already uses tap to pay for things at participating vendors. Here in Canada, it's rare to come across a location that doesn't accept tap. That includes restaurants and cafes. This eliminates the need to input a PIN for verification. It's quick, easy and secure-ish. The problem being if someone happens to get a hold of your card, they can buy things up to a certain value without having to provide any kind of authentication. This being the major drawback of this system. There is also the threat of bad actors using RFID scanners to pickup your credit card information right out of your wallet. By all means be aware of this, but I won't be going deep on this subject.
This is where Apple Pay will differ. Once you setup your credit or debit card on Apple Wallet, you'll be able to make purchases by NFC (near-field communication) or more commonly referred to as tap to pay. Let's consider the same scenario as before, where someone gets their hands on your phone. If they cant unlock your phone, they can't make purchases with your phone. That in itself is a huge security advantage over simply using your card. You must unlock your phone in order to pay with a card in your Apple Wallet. That also includes paying with the same method on your Apple Watch.
When Apple first released this feature I used it at my local grocery store. The cashier looked at me with wonder and confusion at first and asked: Aren't you worried about someone stealing your phone? My response was if someone stole my phone, they'd also need my face to pay for anything, and if that's the case, I have far bigger problems than someone using my phone to buy things. Bottom line here, is that if your credit card gets stolen, it can be used without intervention to pay for items. If your phone get's stolen, they'll need your PIN or your face to unlock the phone.
To make things even more secure, Apple also does not share your credit card info with vendors. If you pay with your credit or debit card, the vender can see your information in plain text. While in most cases this is normal it does rely on the vendor to secure your information. In the case of Apple Pay, Apple creates a token, that is encrypted which is understood to represent your card's information without revealing any usable information to would be bad actors.
Tokens are machine generated, and encrypted codes used to verify things like, your identity, credit card information, anything that needs a high level of security. This is a very secure and robust system that is far better than sending your information in plain text.
Once you have your card of choice added and verified in your Apple Wallet, a double click of the power button will attempt to open your Apple Wallet, but your phone will need to be unlocked either by FaceID, PIN or on older devices, TouchID. Once this is complete, the card you've marked as your default payment method will appear, and will prompt you to Hold your phone near the reader to complete payment. The vendor does not need to advertise that they accept Apple Pay, just that they accept the card you are trying to use. It's that simple. You can also use your Apple Watch to perform the same action. Just double press the side button to bring up your Apple Wallet.
You can read more about Apple Wallet directly from Apple