Tephra is the discharge that comes out of the volcano. It comes in three different forms, accessory, accidental, and juvenile. Accessory is made up of the volcanic cone that is shot everywhere when the volcano erupts. Accidental is sub-volcanic rock. It is carried up from the mantle or the lower part of the crust.
Juvenile is made from pure magma.
When the volcano erupts, shards of magma are shot miles high. Tephra gets a different name according to its size and weight and color. There are cinders, which are small glassy rocks. There are different types of ash. Juvenile and accessory are the origins.