Shield volcano a volcano with very gentle slopes composed almost entirely of very fluid basaltic magma. Pyroclastic is a general term for rocks and deposits generated by explosive eruptions. Pumice is a rock composed of little more than the sides of tiny bubbles. It can be less dense than water. Pyroclast is a general term for a fragment of of rock ejected during an explosive eruption.
Pumice is an example of a pyroclast.
Tephra is a deposit of pyroclasts, that have not yet turned into a rock. Pumice is coarse tephra, ash is fine-grained tephra. Can be built into a tephra cone. Pyroclastic flow a mixture of ash, tephra, and other debris that flows down the mountainside. Common on stratovolcanoes where eruptions melt snow and cause landslides.