Suppose we have five blue pairs of socks and five black pairs of socks in a drawer. We pull out one pair, which may be blue or black, so now there are nine pairs of socks left in the drawer. What is the probability that the second pair of socks will be black?
The answer to this question is--it depends. If the first pair we pulled out is black, then the drawer is left with four black pairs out of nine, so the odds of pulling black socks the second time is 4/9. If the first pair we pulled out of the drawer is blue, then there are still five pairs of black socks left, so the probability of pulling blacks socks on the second draw is 5/9.
The second draw of socks is a dependent event. It depends on what happened on the first draw.