A treatment is an action that is applied to an incoming call. The treatment is applied per phone number, so multiple numbers can perform different actions. There are quite a few treatments available for inbound phone numbers.
Available Number - an unassigned telephone number.
User - routes to a user specified.
Conference - routes to a conference bridge specified.
Call Queue - routes to a specified call queue.
Auto Attendant - routes to a specified auto attendant.
Voicemail - routes to the specified user’s voicemail box.
SIP Trunk - routes to a specified SIP trunk.
Available numbers are numbers that have been assigned to your account, but have not been assigned a specific function.
The User treatment routes a number directly to a user. Typically, this is used with DIDs assigned to specific users versus a general business number.
The Conference treatment routes a number directly to a conference bridge.
The Call Queue treatment routes a number to a Call Queue. Call Queues include a traditional First Available call queue as well as Hunt Groups, where the call will ring a group of people at the same time.
The Auto Attendant treatment routes a number directly to an Auto Attendant, where a user can then select options from the Auto Attendant.
The Voicemail treatment routes a number directly to a specified users' voicemail.
The SIP Trunk treatment routes a number to a SIP trunk, if one is defined for your organization.