Benefits of using Deployments

Define Common Input Parameters
Deployments provide a useful way of managing a common group of instances.  For example, if you set common input parameters at the deployment level, all servers in the deployment will inherit the same parameters unless they are overwritten at the server level.   (Input parameters that are defined at the deployment level will overwrite the values that are defined at the ServerTemplate level.  It's useful to define common input parameters at the deployment level for all servers such as AWS and database credentials.  You cannot define Inputs for the Default deployment.  You can only define deployment-wide inputs for a deployment that you create.  For a description of all input parameters, see the List of Inputs.

Multiple Deployments
Deployments are especially useful for creating unique or identical work environments.  Remember, deployments are completely FREE.  You only have to pay for server usage.  Therefore, you might want to use deployments to organize custom server environments (production, staging, testing, backup, marketing, etc.).  Each deployment can have different users with different permission rights.  

Clone Deployments
The ability to instantly clone a deployment with one click is a very simple, but very powerful feature. Now you can create an exact copy of an existing deployment.   For example, clone your "staging" deployment for your quality assurance team so they can perform GUI and regression tests without impacting the developers' environment.  Create a clone of your production-ready deployment as a backup that will be ready to launch in a different availability zone if problems arise.  See Designing Failover Architectures on EC2.  Remember, in the cloud, you are no longer limited by hardware resources.  Now you can create working environments that are always available for you on-demand.

Lock a Deployment
You should lock a deployment in order to prevent a deployment from being deleted. It also prevents servers from being removed from a deployment, but it does not prevent a user from adding servers or performing actions on any existing servers, such as launching/stopping servers.