What is a whiskey flight?

Could you please elaborate on the concept of a whiskey flight? Is it similar to a wine tasting where one samples different varietals or expressions? If so, how does it differ and what are some of the key factors to consider when selecting a whiskey flight? Additionally, what are some of the most popular whiskey flights and what sets them apart from one another? Lastly, how does the experience of enjoying a whiskey flight compare to simply drinking a single whiskey neat or on the rocks?