It's really confusing.Can any one please explain to me, how come the USB-C is the same as thunderbolt? I thought they are different just like Firewire and USB are different.
Plus, I have never seen a thunderbolt device, what can it do that USB 3 can't?
You need to distinguish between the shape of the physical commector, and the protocol over which the connected devices communicate with each other (this would mean they send data over different pins, the rate at which they send data might be different, different power requirements, different ACK formats, etc).
So far, for the most part in the history of computers, each connector usually only supported 1 protocol. So you could tell a device was USB just by looking at the connector at the end (well, even the latest USB connectors, however, supported multiple protocols, such as USB 2 and USB 3, but this wasn't an issue because they were backwards compatible with each other).
The latest connector however, the USB - C connector, has been extremely popular and adopted by other protocols as well. In this case Thunderbolt.
So essentially, Apple is able to deliver USB 3.x as well as Thunderbolt over the same port because it chose the USB-C connector for Thunderbolt.
TB3 is a lot faster than USB. I believe the latest USB spec is at about 10 Gbps while TB3 is at 40 Gbps.
The problem is that the same connector is gonna lead to amass of confusion for most users. Apple has also decided to do away with markings, and/or color schemes which the PC side had adopted which will increase user's confusion.