Learning something new takes a lot of time, and time is scarce. We couldn't india mailing list even remember it all if we had to store information about each thing separately! So we categorize. Categorizing was already happening in the time of the Greeks. Grouping or categorizing things helps us get through the day and understand the world around us. The average of such a category is the stereotype or prototype (Tversky & Kahneman, 1981). Basing our opinion on this prototype creates the representativeness heuristic. We know a category, we encounter something from that category that resembles the prototype, and we intuitively make a decision based on our knowledge. Because there has to be a connection between that, right?
Examples in practice
If you see a bull running, then based on your knowledge about the category of bulls, you know that you had better stay away, because this bull is also likely to be dangerous.
If you see a product from an unknown brand listed that is very similar to a well-known brand, you will subconsciously think it has similar performance when you don't have more information available.
Dating sites: the first impression you have of someone is often based on stereotypes.