Electricity is the flow of

The definition of electricity is the flow of charge. Usually our charges will be carried by free-flowing electrons.

Negatively-charged electrons are loosely held to atoms of conductive materials. With a little push we can free electrons from atoms and get them to flow in a generally uniform direction.

A closed circuit of conductive material provides a path for electrons to continuously flow.

The charges are propelled by an electric field. We need a source of electric potential (voltage), which pushes electrons from a point of low potential energy to higher potential energy.