Superlatives are the highest form of something and must be used when comparing three or more things. Like the simple comparatives, we use “-est" for short words and words like “most," “least," “best," etc. for longer words. Look at these examples
Mike is smarter than Fred in class, in fact he is the smartest student I have.
Paris is better than most cities, it is perhaps the best city in the world.
The New York Times recently reported that Joyce was the finest writer of the twentieth century.