If you’re looking to find out which computers support the Apple Thunderbolt to Gigabit Ethernet Adapter, where you can connect it, the requirements for using it, etc., Apple released a handy FAQ that answers all these questions, and more.
If you’re curious to know which Macs support this adapter, you should be happy to learn that all Thunderbolt-equipped systems are a go, so long as you have OS X Lion v10.7.4 or later installed. Macs released prior to June, 2012 that also boast a Thunderbolt connector will require Thunderbolt Software Update 1.2.1 to use this adapter.
You can connect this adapter to external devices, as well as directly to the port on your Mac. And, if you’re "daisy chaining" multiple devices, Apple says that at least one computer on the Thunderbolt chain needs to act as a host. This and much more can be found here, in the Apple Thunderbolt to Gigabit Ethernet Adapter: Frequently Asked Questions.