Adverbs of degree can describe adjectives or other adverbs.
+ | a little/a bit | shy (adjective) |
++ | pretty/quite | shy (adjective) shyly (adverb) |
+++ | very | shy (adjective) shyly (adverb) |
++++ | really | shy (adjective) shyly (adverb) |
+++++ | extremely | shy (adjective) shyly (adverb) |