A posteriori knowledge refers to information that is gained through experience or observation rather than through theoretical reasoning. This type of knowledge is often associated with empirical evidence, meaning it relies on data collected from the real world. For example, knowing that water boils at 100 degrees Celsius at sea level is a piece of a posteriori knowledge because it is derived from experimental observation. In contrast to a priori knowledge, which is independent of experience, a posteriori knowledge requires sensory input to be validated. This distinction is important in fields like philosophy and science, where understanding the basis of knowledge can influence theories and conclusions.