The power state of a device encapsulates what that devices’ power budget is, and what it is currently doing with this power. It is often internally represented by one or more finite-state machine abstractions.
For example, a typical USB Type-C Power Delivery battery charger usually has a single state machine, whose nodes and edges correspond to states defined in the Power Delivery spec. A laptop, which can potentially draw power from at least one source and may provide it for a number of others, can have a variety of power states, potentially encompassing more than one finite-state machine. Devices like USB hubs and Power-over-Ethernet (PoE) network switches may have a power state across the whole device, or an array of per-port independent power states, a hybrid approach, or a novel representation of its state.
For further reading, have a look at the state-machine tag.
