DPMA uses eight internal concepts:
A Network is a set of configuration parameters that are specific to a network location. At each location, the address to network services may be different. In order to accommodate this, a network is defined and then applied to a Phone.
A Phone is a set of configuration parameters that represent the device on your desk. A Phone is abstracted because in most cases, it represents an individual user's configuration, e.g. Bob's Phone. Bob's Phone has line keys that are specific to Bob, it has a contacts list that's specific to Bob, it has Rapid Dial keys that are specific to Bob.
A Line is a key on phone that is mapped to an Asterisk SIP identity ("friend," technically, since that's a better way to go if you want to assign more than one SIP identity to the same physical device) and labeled in a particular way. Because, in Asterisk, there's a one-to-one relationship between physical device and SIP identity, a Line also maps one-to-one to a SIP identity, since it will only appear on one physical device at a time. A line is applied to a Phone.
An Application is a set of configuration parameters specific to the operation of a particular application on a Digium phone. An application is applied to a Phone.
A Ringtone is an audible tone used when a Digium phone is receiving a call. A ringtone is applied to a Phone.
An Alert is a type of ringing, comprised of a triggering info message, a ringing type, and a Ringtone. An alert is applied to a Phone.
A Firmware defines a phone firmware version to be applied to a Phone.
A Translation defines a set of mappings to be consumed by an application that is applied to a Phone.