Electricity is a general term for a wide range of events resulting from the presence or flow of an electric charge. These events could be things commonly known such as lightning or static electricity, but an other event possible could be electromagnetic fields. People have been aware of the shocks they received from electric fish and eels for a long time. Old Egyptian texts found named these fish as 'Thunderers of the Nile' and they were proclaimed as the 'protectors' of all fish. Later on, Ancient Greek, Roman and Arabic physicians wrote about these fish. They knew of the numbing effect of the shocks, and they knew the shocks could move with conducting objects. These electric fish were used as medicine to cure gout or headaches. The theory was that the sudden shock would shake away the sickness. Thales of Miletos made a series of observations around the year 600 BC concerning static electricity. He believed the static was because the objects he rubbed became magnetized because of friction. After him, electricity was no more than an abstract curiosity for millennia until 1600. In the early 19th century, the work became more precise and extensive experiments and observations were made. In the late 19th century, electricity was discovered and it became a tool in science and modern life instead of a scientific curiosity. People like Nikola Tesla and Thomas Edison showed up and electricity became a necessary force for the Second Industrial Revolution.
Electricity comes from atoms. The protons and neutrons create the center, the nucleus. The protons are positively charged and electrons, which rotate around the nucleus, are negatively charged. The neutrons, hence the name, are neutral. They are not charged. The actual electricity comes from when the electrons move from one atom to the other. Negatively-charged electrons are always attracted to positively-charged protons.
Some atoms are excellent at conducting because there are tracks which the electrons follow. The electrons mostly stick to the closest track to the nucleus because it requires less energy. If the track the most extended to the outside is clear enough of other electrons, the electrons can jump from one track to another and exit their previous atom to enter a new one. These atoms are Conductors. If the track isn't clear or if the atom holds on tightly to it's electrons, the electrons cannot move and no electricity is created. Another reason why some atoms conduct better than others is because of their Atomic Number. This number is written on the periodic table of the elements, and it basically tells you how many protons are in the nucleus of one atom from that element. The positively-charged protons attract negatively-charged electrons, making the passing from one atom to the other more tempting and once the electrons are moving, the attraction makes it easier for them to move.