I don't know NetBeans so I don't know why it failed to configure your database driver.
A client/server environment is an environment in which multiple applications connect to Derby over the network.
Derby runs embedded in a server framework that allows multiple network connections. (The framework itself starts an instance of Derby and runs in an embedded environment. However, the client applications do not run in the embedded environment.)
You can also embed Derby in any Java server framework.
See the Java DB Server and Administration Guide for more information on how to run Derby on a server.