Simplify the following text for a Grade 11 native English-speaking person.
Original: An electro-diesel locomotive is one that can operate either from an electrical supply , such as overhead catenary or ( in this case ) an energised third rail , or from an onboard diesel engine .
Simplified: An electro-diesel locomotive is one that can operate either from an electrical supply , such as overhead catenary or an energized third rail , or from an onboard diesel engine .