Electronics Basics: Conductors and Insulators
Electronics is the branch of science, engineering and technology dealing with electrical circuits, so it helps to understand the principles of conduction and insulation, before delving into building electronic circuits.
Some elements don't hold on to their outermost electrons very tightly. These elements frequently lose electrons or pick up extra electrons, and so they frequently get bumped off of neutral and become either negatively or positively charged. Such elements are called conductors. The best conductors are the metals silver, copper, and aluminum.
Other elements hold on to their electrons tightly. In these elements, it's hard to pry loose an electron or force another electron in. These elements almost always stay neutral. They're called insulators.
In a conductor, electrons are constantly skipping around between nearby atoms. An electron jumps out of one atom — call it Atom A — into a nearby atom, Atom B. This creates a net positive charge in Atom A and a net negative charge in Atom B. But immediately, an electron will jump out of another nearby atom –Atom C — into Atom A. Thus, Atom A again becomes neutral, and now Atom C is negative.
This skipping around of electrons in a conductor happens constantly. Atoms are in perpetual turmoil, giving and receiving electrons and constantly cycling their net charges from positive to neutral to negative and back to positive.
Ordinarily, this movement of electrons is completely random. One electron might jump left, but another one jumps right. One goes up, another goes down. One goes east, the other goes west. The net effect is that although all of the electrons are moving, collectively they aren't going anywhere.
They're like Keystone Kops, running around aimlessly in every direction, bumping into each other, falling down, picking themselves back up, and then running around some more. When this randomness stops and the Keystone Kops get organized, the result is electric current.