About Private LAN
If you have more than one Dedicated Server in the same account, a private LAN allows you to configure the servers to "talk" to each other via their Network Interface Cards. This means that data can be transferred between the servers without using any bandwidth included in your account.
For example, you could have your e-commerce website on one dedicated server, and the SQL database the site queries on a 2nd dedicated server. This spreads the load of your busy site across two servers and will not use up your servers' bandwidth in resolving database queries.