Breadboards are used for testing and experimenting with electronic circuits. I find them extremely convenient because they require absolutely NO soldering, and you just have to plug the component into the little holes that are provided on the breadboard.
Iguana Labs gave a few of these pictures and explanations. Thanks Iguana Labs!
Step 1: The Breadboard Connections
The top and bottom rows (the rows indicated by the blue) and are usually the (+) and (-) power supply holes and these move horizontally across the breadboard, while the holes for the components move vertically Each hole is connected to the many metal strips that are running underneath.
Each wire forms a node. A node is a point in a circuit where two components are connected. Connections between different components are formed by putting their legs in a common node. On the bread board, a node is the row of holes that are connected by the strip of metal underneath.
The long top and bottom row of holes are usually used for power supply connections.
Step 2: Connecting the Components
For chips with many legs (ICs), place them in the middle of the board so that half of the legs are on one side of the middle line and half are on the other side.
A complete circuit might look like the one below.
Step 3: Building a Circuit on the Breadboard
When you use switches or potentiometers, you must use single-core plastic-coated wire of 0.6mm diameter (the standard size). Stranded wire is not suitable because it will crumple when pushed into a hole and it may damage the board if strands break off.
The rest of the circuit is built by placing components and connecting them together with
jumper wires. Then when a path is formed by wires and components from the positive
supply node to the negative supply node, we can turn on the power and current flows
through the path and the circuit comes alive.