Explanation:
Replacement means the probability of each trial is the same (the trials are independent).
For example, let's say you have a standard deck of 52 cards, and you want to find the probability of drawing a queen card twice.
There are 4 queens, so the probability on the first draw is 4/52.
You then replace the queen, so there are still 4 queens in the deck. So the probability on the second draw is still 4/52.
The total probability is the product: 4/52 × 4/52 = 1/169
If you didn't replace the queen after the first draw, there would have been 3 queens in the deck, and the probability on the second draw would have been 3/52.