Adjectives describe nouns: How is something?
The funny costume

To compare two things you say: The costume is not as boring as last year. Or less boring than or more boring than.

To compare with adjectives you use the ending -er and -est for adjectives with one syllable or adjectives ending with -y, -er, -ow or -le: funny – funnier – the funniest

For all other adjectives you use more & the most: expensive, more expensive, the most expensive.

Adverbs describe verbs: How is something done?

Add the ending -ly to the adjective
Cut the pumpkin carefully.

!NO -ly: sense verbs!

It looks good. It smells fantastic.

Adjectives: How is something?
Describing: the ... costume
Comparing: (not) as ... as; more ... than

Adverbs: How is something done?
Form: Adjective + -ly
Exception: sense verbs