A Call is the verbal component of a combat attack "5 Silver Lightning Lesser Confine" to given a maximumally complicated example. This blow does Five Points of Damage, it has the Silver attribute and can affect characters who take special damage effects from silver (the other common attributes are Normal and Magic), it has the elemental attribtue Lightning and thus does more or possibly less damage to creatures affected differently by Air attack (Lighting). (There are 13 possible elemental attribute.) The final part of this call is a spell carrier, in this case the attack is carrying the spell "Lesser Confine". If the blow is good and if it also does at least one point of body damage then you suffer the effect if a Confine but becuase it is Lesser only for 10 seconds.
The Call must be full spoken during the attack and a second attack can not be made until it is completed. It is an intentional control on the pace of combat. If you are using Conversational Combat where the calls are constant and thus not repeated each time you must still keep your rate of attack the same.
All non-ranged attacks must be delivered in a clear, conversational tone of voice (no yelling). Further, once you have announced your damage to your opponent, there is no need to continue announcing it until another opponent appears.
Incant, short for Incantation, is the verbal component of a spell such as "I call upon Chaos to Cause Light Wounds 5". It must be full spoken before the spell packet (representing the summoned magical aura) is touched to the target or thrown at them and the packet must be thrown or touched within 3 seconds.