Calculates the probability of two (or more) events BOTH happening. When the events are independent of each other, P(B given A)=P(B) and this conjunction rule reduces to the restricted one.
For example, consider the probability of picking two aces from a deck of 52 cards without replacement. From simple probability, the chances of getting an ace on the first draw is 4/52 or 1/13. P(SECOND CARD IS ACE given that FIRST CARD IS ACE)=3/51.
Answer: 1/13 * 3/51 = 1/221