At a high level, Pantavisor is just in charge of two things: container orchestration and communication with the outside world.
The software that is running in a Pantavisor-enabled device at a certain moment is called a revision. A revision is composed by a BSP and a number of containers. Pantavisor is able to go from the current running revision to a new revision in a transactional manner.
Revisions, as well as other relevant data, are stored on-disk in the device to make them persistent.