We use the comparative and superlative forms of adjectives when we are comparing things.
The black and tan puppy was cute, but the black puppy was cuter (comparative) and the brown puppy with blue eyes was the cutest (superlative) of all.
For adjectives with one syllable we usually add 'er' and 'est' to form the comparative and superlative, but for adjectives with three syllables or more we use the words 'more' and 'most' instead.
Apples are delicious, but bananas are more delicious and strawberries are the most delicious.
Adjectives with two syllables are more difficult because they can follow either rule.
Most adjectives ending in -y, -le and -ow add 'er' and 'est'.
noisy noisier noisiest
gentle gentler gentlest
narrow narrower narrowest
Most other two-syllable adjectives add 'more' and 'most'.
careful more careful most careful
anxious more anxious most anxious
Don't forget that some adjectives don't follow the rules at all!
good better best
bad worse worst
far further furthest