Electricity is is the phenomena that a electric charge (protons) run from the positive part of a circuit to the negative part. Electricity is thus a way to transmit and store energy. It is not a source of energy itself.
The mains electricity grid
The mains electricity grid makes it possible for energy produced in large remote nuclear, hydroelectric or Coal fired power stations to be transmitted accross the country to be used in homes, factories and offices in far away cities.
A nationwide or continental electricity grid also means that remote alternative energy sources, such as wind or Wave power, can be brought to users in cities. A continental grid can also be used with alternative energy sources whose capacity varies depending on the tides and the weather so that a shortfall in one area can be made up by supplies from elsewhere.
Note that the Carbon rating of electricity (the number of kilograms of carbon dioxide released into the atmosphere for each kWhr of electricity) varies depending on the ratings of the power stations supplying the grid.
All of this however depends on a large infrastructure of extra high voltage transmission lines, large power stations, users being concentrated in cities. A more appropriate energy infrastructure would depend on local energy sources, controlling the loads to match the available power.
Electricity can be a part of such a local power system, being used as a medium to convert wind, solar, small hydro, biogas into one common form which can more easily be used for lighting, communications, pumps and which can be stored in Batteries.