a little=a little bit +形容词
a little可以直接作定语修饰名词,而a little bit需要加of才能修饰名字.
在肯定句中修饰动词、形容词、副词和比较级时,两者可以互换,表示"一点儿"的意思.I speak a little French.I speak a little bit of French.Jack is a little selfish.Jack is a little bit selfish.