In probability theory, a dependent event is one where the outcome of one event affects the outcome of another. For instance, consider drawing cards from a deck without replacement. The outcome of the first draw influences the probabilities for subsequent draws. If you draw a red card first, there are now fewer red cards in the deck which alters the odds for the next draw.
On the contrary, an independent event would be like flipping a coin; the outcome of one flip does not change the odds of the next flip. Thus, a classic example of a dependent event is drawing two cards from a deck in succession, where the first draw impacts the possibilities of the second.