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Lets say you have 10 agents that most days comfortably handle most of your calls within you your defined Service Levels (the amount of time you have to answer a call). Every now and then you your team gets flooded with calls when something unexpected occurs and so they need some help handling all of the extra calls. Thresholds allow you to define a Secondary team of Agents that can help your primary team during these peak periods.
The Secondary Team will ONLY recieve receive calls if some threshold is breached. Once the threshold is no longer in breach the Secondary Team will no longer recieve receive calls at least not until the next breach.
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Your Primary team of Agents should be added to an 'Immediate' Threshold. With an Immediate Threshold, as soon as a call arrives in the Queue any Available Agent in associated with this Threshold will be rang (according to the Ring Strategy).
The Immediate Threshold also provides a 'Priority' option. The priority allows you to further split you your primary group by creating multiple Immediate Thresholds with different priorities and members. If you have two Immediate Thresholds one with a priority of '0' and the other with a priority of '1' then when a call arrives in the queue it will be immediately allocated to any Available agent that is a Member for the Priority '0' threshold. If there are no Agents Available in the Priority '0' threshold then the system will immediately allocate calls to Agents which are Members of the Priority '1' threshold.
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The Call Count works the same as SLA except that the threshold is the no. of calls waiting in the queue. If the 'Call Count' is 10 and more than 10 calls are waiting in the queue then Agents which are Members of this Threshold will be considered Available (subject to them being logged in and not in Wrap and not Paused).