Heraldry usually involves the creation and registration of armorial bearings, or devices. In the SCA, heralds are also responsible for keeping track of awards, researching accurate medieval names, compère-ing tournaments, running ceremonies, and a multitude of other things.
These activities are usually divided into two main categories. Book heraldry involves anything to do with the registration of names and devices, and the organisation of ceremonies. Voice heraldry is announcing things.