Atlantech's contact center service makes a useful example, because the list on its page maps onto that core. The page names voice and web chat licenses, skills-based routing, an IVR, queue callback, real-time wallboards, supervisor control, historical reporting and CRM integrations. Follow one call through the system and each item turns out to have a job.
The caller first reaches the IVR, the recorded menu that asks what they need. Pressing 2 for billing sorts the call before any agent is involved. That choice places the call in a skill group, which is the name Xima uses for a queue of contacts that need the same kind of agent. Atlantech's service runs on Xima. Skills-based routing then offers the call to an agent who belongs to that group. Xima's skill settings rank the groups from 0 to 10 for an agent who belongs to several.
If nobody is free, the call waits, and the queue needs rules for a long wait. Xima gives each skill a queue timeout, an overflow destination and a cap on the number of waiting calls. Queue callback lets the caller hang up and keep a place in line. Without those settings, a caller in a long wait has two choices: keep holding until an agent answers, or hang up.
While this is happening, a wallboard shows supervisors who is waiting and which agents are busy. Atlantech's page says supervisors can update an agent's status and force a call to a specific agent. After the call, historical reporting keeps what the page calls a cradle-to-grave record of it. The page also lists CRM integrations, which can connect a call to the customer's account record once they are set up.
Each of those features did a job on this one call. When one is missing, the customer feels it as a call sent to an agent who can't help or a long hold with no alternative. We go further into the sorting step in what routing is in a contact center and into the distribution step in what an ACD is.