en:faq:what_s_the_difference_between_account_agent_and

Account: mainly used for management systems, including system admin, team admin and users
- System admin: to manage the entire system, have full privilage in system.
- Team admin: to manage a team, have full privilage in a team, including accounts, seating, and PBX and so on.
- User: the basic unit in astercc, and is charging unit, a user may include zero or more agents and devices.
Device: device can be divided into internal and external extension, between devices, they can reach each other by dialing extension number.
- internal device: internal device is device connect to the asterisk, such as SIP, IAX or DAHDI (ZAP), internal device can be reach by extension number, and when internal device dial an outside line, the system will calculate the costs will be incurred to the user which belongs to.
- external device: refers to an ordinary telephone number, such as mobile or landline, external device can only receive calls.
- extension: Each device will have an extension number, internal device can dial the extension number to reach the others, for example, extension 5000 is an external device (number 041139735857), then some internal device dial 5000, the system will try to call the number 041139735857.

When external device receive calls from the system, the costs incurred will be recorded in the corresponding accounts.

Agents: for call center operations, including inbound and outbound campaign, before work, agents will first be allocated to different agent groups and then assigned to different campaign, when adding agents, we need to choose an device for the agent, or input an outside number.