Electricity is the flow of electrons through a conductor. Materials that conduct electricity easily have a weak hold on their outermost electrons, allowing them to move easily from one atom to another. When an electron moves to an adjacent atom, it displaces another electron, and this flow is electric current.
The flow of electrons is caused by the electrical charge of particles. Electrons have a negative charge, and protons have a positive charge. When an atom loses an electron, it becomes positively charged. When an atom gains an extra electron, it becomes negative. Since like charges repel, an electron moving from one atom to another displaces other electrons, pushing them further down the line.
Since electric current is caused by the flow of electrons, in a metallic conductor, it is the flow of negative charges through the material. However, in other materials, such as semiconductors, the charge carried can be positive or neutral. Benjamin Franklin, in his studies of electricity, theorized the possibility of positive charge carriers and created a standard that electrical engineers use to this day. To simplify electrical diagrams, the current is shown to flow from the positive to the negative pole, even though in many cases the negative pole is the originator of the current.