If you’ve paid close attention to labels on any electric products, devices, or appliances, you may have noticed a small mark with the initials “UL” on it. It’s not something associated with a particular company or brand of products, and is one of those things that once you know it’s there, you start noticing them all over the place. But what does the “UL” mark mean? Here’s what to know.

UL stands for Underwriters Laboratories, which describes itself as “a not-for-profit organization dedicated to public safety.” Founded in 1894 to promote safe living and working environments, UL’s primary function was, and continues to be, product safety testing and certification. Although there are other organizations that offer the same safety testing service, UL is the best-known.

The first iteration of the UL label came out in 1906, and certified that individual products have been tested, and met the organization’s safety standards. It means the same thing today. Seeing “UL Listed” on the label of a product assures you, as a consumer, that it will work as expected, and doesn’t pose a safety risk to you. In other words, if you have to decide between purchasing an item with a UL label versus the same type item without that mark, opt for the one with it.

Let’s say you purchase a refrigerator. You may notice “UL Listed” on the label affixed to the appliance’s power cord. And while you were at it, you also bought a washing machine, which has “UL Recognized” stickers on several individual parts. What’s the difference between the two?

Lock, unlock your door from anywhere Open remotely via Bluetooth or Wi-Fi with the eufy Security app, or by using either the electronic touchscreen keypad or the key. A built-in sensor detects when your door is closed and locks it automatically behind you, keeping your home secure even when you’re in a hurry or your hands are full. Certified by the American National Standards Institute to work after locking and unlocking 250,000 times, Smart Lock can easily handle the daily comings and goings of a busy household.

According to UL , “UL Listing means that UL has tested representative samples of a product and determined that the product meets specific, defined requirements.” Meanwhile, “UL Component Recognition means that UL has evaluated components or materials intended for use in a complete product or system. These components are intended only for end-use products that may be eligible for UL certification.”

So basically, “UL Listed” means they tested the product (as a whole) and it works safety, while “UL Recognized” labels are place on specific parts of a product that are tested.