Basically, the smartthings system uses a driver so that the hub knows what messages to send to a specific device, and how to read the responses. This is very similar to a printer driver for your computer.
The platform provides a number of Edge drivers which will be automatically installed if the “fingerprint” of the device matches one. But these often provide only basic functionality. It’s quite common for device manufacturers or community members to create custom edge drivers, which expose additional advanced functionality.
Here’s the community FAQ on edge. It has most of the details and terminology you should need. 
FAQ: I have no idea what Edge is. Is that a new developer tool? (2022)