NOT inverts the results. On the first rung in the example above, if P0 is ON then P5 will be OFF.
AND is performed on two registers when they are placed horizontally beside each other on the same rung. On the second rung in the example above, both registers P0 and P1 must be ON in order for P5 to be ON.
An OR operation is performed when two registers are placed vertically beside each other on the same rung. On the third rung in the example above, when either P0 or P1 is ON, P5 will be ON.
When two or more AND or OR operations are used on a single rung, as illustrated in the following example, it is called a BLOCK AND or a BLOCK OR.