We sometimes use adjectives to compare things.
We can add er to most describing words when they are used to compare two things.
The giraffes are taller than the zebras.
The little squirrel is higher than the dog.
The hare is faster than the tortoise.
We can add est to most describing words when they are used to compare more than two things. We add est when something is the MOST of something.
The giraffe is the tallest animal.
The blue whale is one the of the world's largest animals.
She is the fastest player on her team.