a lot 是副词,用在句尾表示程度.
如：We enjoyed a lot.我们感到很尽兴.I practiced a lot.我近来锻炼很用功.
a lot of 用在名词前,则表示很多.
如：a lot of people 很多人.a lot of cars 很多车 等.这个比较好理解.
much 用在比较级前面表示程度,“ .多了”、“更加”
如：She's much quieter.她安静多了.We have much more confidence.我们有更大的信心.
简单来说就是：比较级前面只能加much,不能用a lot.a lot是副词,用在句尾.a lot of 后面加名词,表示数量多.

a
lot可以修饰比较级。修饰比较级的常用词和短语有：much,
even,
still,yet,
(by)
far,
a
lot,
a
great
deal
,
twice,
five
times
,
a
little,
a
bit,
rather
等。