Battery electric vehicles get all of their energy from an electrical circuit. This allows them to operate at a very low cost - electricity generally costs the equivalent of less than $1 per gallon of gasoline. When the energy is provided by a utility with low cost EV rates, the cost can be as low as $0.60 per gallon equivalent.
Plug-in hybrid vehicles use electricity for the first 10-126 miles of travel and then automatically switch over to the gasoline engine. PHEVs offer essentially unlimited range, with the environmental and cost benefits of an EV for most local in-town driving, like a daily commute.