Using a serializable class to act as data carrier, grouping related attributes, forming a composite value and working as a return type from remote business method. Also known as Value object.
In the J2EE server, the client tier may make several calls to retrieve data from the enterprise bean. Even in the same machine, the every call from the client tier to the server tier is a remote method call. Think about use Transfer Object design pattern to retrieve related attributes and return a single object instead of each call just for retrieving a single attribute value. The transfer object is passed by value to the client. All calls to the transfer object instance are local calls to the client, so such design saves a lot of network traffic.
Let's say that you have a remote banking system. If the user has five requests one time, you should design your system to give response once, not five times. You may need to group all return values from these five requests to an object carrier and then return to client just once. Once the client program receives the instance of this object, it invokes the accessors and gets value to display. The total network traffic for one user just once.