Adverbs vs. Adjectives

Adjectives

Adjectives describe nouns (things).

• My dog is slow.

Slow is an adjective since it describes the noun (my dog).

• How is my dog? Slow

Adverbs

Adverbs describe verbs (actions).

• My dog eats slowly.

Slowly is an adverb since it describes the way my dog eats.

• How does my dog eat? Slowly.

Some adverbs are used to modify an adjective.

Adverbs that do this are: very, extremely, really, totally, absolutely, quite, fairly, well. These are normally placed before the adjective.

• He is very rich.
• They are extremely happy.
• She was totally crazy.
• My dog is well trained.

Adverbs and Adjectives with the same form

There are a number of adjectives / adverbs that take the same form. It therefore depends on the sentence context as to whether it is an adjective or an adverb.

The adjectives / adverbs that take the same form include:
fast, hard, early, late, high, low, right, wrong, straight and long.

• Adam has a fast car. (Adjective)
  
• Adam speaks fast. (Adverb)

Good vs. Well

Good and Well are two words that tend to create confusion for learners of English.

Good is an adjective
Well is an adverb.

• She is a good singer.
• She sings well.

Though sometimes we use well as an adjective when we are talking about health and well-being.

• A: How are you today?
  B: I'm well, thanks.

(I'm well is a better and more common answer to this question than 'Fine' or 'Good', although these are also reasonably common.)