This is the inside of a bread-board. The rows are connected with metal strips, The center of the breadboard separates the two sides of the rows. And the only columns that are connected are call busses, or Rails. They run along the sides of the bread boards only.
1.
The breadboard connects in the rows [pink marks].
The board does not connect the left side to the right side [where the red squiggly line is.
2.
The power rails are all linked together on the side. [green and orange lines. In the photos below, nothing is connected to these lines.
3.
If we follow the pink/purple highlighted trace you can see how the bread board is connected to the switch. The battery is conected to the bottom of the board. It is conected to the two rails on the left side, of the board. Because that is conected all down the left side the wires conected to the button and the resistor make conection to the battery. The same as if you conected the wires directly to the battery.
4.
The left side shows proper ways of connecting the Led's.
[A, C]
The right side is the INCORECT way of connecting the led's.
B: is incorrect because the led leg is not connected in in the wrong row of the resistor.
D: is incorrect because the middle of the bread board is separating the two sides of the rows.
A
B
C
D
5.
The last example is INCORECT. The led is not connected to anything other then it's self. With the led connected like this the two legs of the led are shorted together. The resistor is connected to nothing in its row, And although the wire is connected in the same column, columns are not connected together. So the red wire is connected to nothing as well.
