UL is a third-party certification company that conducts testing and sets the industry standard for safety for a range of product categories worldwide. 

Depending on the type of device or product, different ratings will be used. For example:

UL Listed – certification of the entire product vs. its components 

UL-Recognized – for components only – not complete, market-ready products

Different marks are used to indicate UL status by country or region, such as Canada, US and Europe.