Can you be more specific? I don't understand the question

I think he is talking about the external power boards which supply the servos with their own supply rather than drawing from the EZ-B.

And that pretty much answers the question too. To avoid browning out the EZ-B, to provide more current and possibly more voltage to servos.

The benefits are many. Servos generally produce more torque with more voltage (check the voltage ratings, this isn't saying to pump 24v in a servo as that will blow it up!). It also allows for the servos to work without taking all 5A that the EZ-B can supply.

Thank You, Rich. That is Exactly what I was talking about. And, thank you, D.J.

Where can I get one of that?! It might be very useful ... Actually, I was thinking about to build something like that from a breadboard... Connecting the signal wire to ez-b and the power to external batteries... Would that work ?

Here are a couple examples:

From HobbyKing

From servo City