Extra Rails adds three additional rails.
The Locking Rail holds the cart on it in place until it receives a redstone signal at which point, it propels the Minecart in the direction it is facing.
The Direction Rail acts like the Golden Rail but it only propels carts in the direction it is facing.
The Teleporting Rail teleports Minecarts on it to the other teleporting rail it is connected to.
To link Teleporting Rails, open the GUI by right-clicking on them and use the 3 color selectors to pick a frequency for the rail. Do the same for the other Teleporting Rail and Minecarts will be able to teleport back and forth.
Note: If there are more than 2 Teleporting Rails on the same frequency, the destination may be random.