A "Critical Period" refers to a specific time frame in development when an organism is particularly sensitive to certain environmental stimuli. During this period, the ability to acquire certain skills or knowledge is heightened, making it easier for individuals to learn. For example, in language acquisition, children are more adept at learning new languages during their early years. If the necessary experiences or stimuli are not encountered during the critical period, it may become significantly more difficult or even impossible to develop those skills later in life. This concept is often discussed in relation to language development, child psychology, and neuroscience.