We just learned more about Samsung's big competitor to Apple Pay

Samsung announced its new mobile payments system months ago, but we just got our first look at how it actually works.

Samsung Pay will be available in the United States starting in September after first launching in South Korea this month.

Samsung's payment system is different than Apple's in one crucial way - it works at standard mobile payment terminals with magnetic stripe readers and NFC terminals. This means you can use Samsung Pay anywhere you can use a credit card, while you can only use Apple Pay and other payment solutions such as Google Wallet at retailers that have NFC terminals.

We've known about this for a while, but Samsung has just told us more about how you'll actually use the service when it launches. If you have Samsung Pay all set up, you can swipe up on the lock screen to select which card you want to pay with, as shown to the right.

This works even if your phone is asleep, so you don't have to turn on the display to start a payment transaction. From there, you can choose to authenticate your purchase by typing in a PIN or by pressing your fingerprint on the home button. Samsung also says its Knox software is integrated into Samsung Pay, which adds real-time hacking surveillance and encryption to the service.

Since Samsung Pay is compatible with both NFC and magnetic stripe terminals, your phone automatically decides to choose one or the other when you're making a purchase.

Here's what you'll see after you authenticate a purchase:

And here's what it looks like when you're actually performing the transaction:

The company announced Samsung Pay back in March when it unveiled its Galaxy S6 and Galaxy S6 Edge phones. Its powered by technology provided by a company called LoopPay, which Samsung acquired in February. This is what makes Samsung Pay work with magnetic stripe readers in addition to NFC.