what do you mean by"

Note: An adverb of degree is usually placed before the adjective or adverb it describes

This means that an adverb of degree is that adverb which describes the intensity of an action, adjective or another adverb. It is placed before an adjective or another adverb it describes. These adverbs answer the question ‘how?’ 

For example: Almost, nearly, quite, just, too, enough, hardly, scarcely, completely, very, extremely etc.