operator(A sign or symbol that specifies the type of calculation to perform within an expression. There are mathematical, comparison, logical, and reference operators)
agent(A person who works for a call center and signs in to an ACD system or who responds to calls routed to him or her by an IVR system. Formal agents may be signed in into UC throughout the day, and they may sign in and out of the ACD system during the day. They are fully aware of their role as an agent and want to be able to see the numbers of calls in the queues they are serving, and so on. Informal agents may not consider themselves as agents, and they don't sign in and out of the ACD system as agents. They do not monitor queue fill levels or other metrics)
