An adjective describes a noun. It comes before the noun.
It’s a beautiful building.
We describe adjectives as gradable and non-gradable.
That means that we can or cannot make them stronger or weaker with an adverb.
For example, we can say
To make the adjective stronger we can use extremely, very, really, a bit.
To make the adjective weaker, we can use not very and quite.
Non-gradable adjectives cannot be made stronger or weaker.
Non-gradable adjectives already describe a quality that is extreme. For example, freezing, exhausted, starving.
You can use really with gradable and non gradable adjectives.
But you can use adverbs such as absolutely, really, totally, completely or utterly to emphasis the adjective.
E.g. It’s absolutely freezing here.