We often use adjectives to compare things
Some adjectives are absolute and so we can only classify things
but not compare things.
Eg: unique, ultraviolet, biological.
We can't say that something is more unique than another thing.
Either something is unique or it isn't.
Some adjectives are extreme adjectives.
With these adjectives we don't use very. Eg: Huge (Not Very huge).
This is because Huge=Very big.