Most Linux distributions (such as Debian) automatically recognize devices and load the appropriate drivers.
If you have a NIC that is not natively supported by the kernel, it means that either the device driver is unavailable or the system cannot associate the device with an appropriate device driver. This can happen sometimes because a new USB device has a new product ID that is not recognized by the system. In this case, you can force the system to use a particular device driver by specifying additional parameters to modprobe. The details of using modprobe is device driver dependent, and is out of the scope of this discussion.