"lots of"和"a lot of"都表示 “许多”或“大量”，在意思上它们是相同的。不过，它们在表达方式和用法上有一些区别：
使用场合
"a lot of"：通常用作书面用语，用在更加正式的场合里。例如：
She has a lot of friends.
There was a lot of background noise at the concert.
"lots of"：比较口语化，用在比较口语的场合中。例如：
I need lots of help with my homework.
They talked a lot about their plans.
修饰词语
"a lot of"：可以修饰可数名词也可以修饰不可数名词。例如：
I have a lot of money.
There is a lot of love in their family.
"lots of"：只能修饰可数名词。例如：
She has lots of books.
They have lots of fun together.
语法结构
"a lot of"：可以独立使用，也可以跟在情态动词或助动词后面。例如：
I really need a lot of help.
They have a lot of fun.
"lots of"：通常跟在BE动词后面。例如：
She has lots of friends.
They have lots of fun.
总结来说，"lots of"和"a lot of"在意思上相同，但"a lot of"更正式，适用于书面语，而"lots of"更口语化，适用于日常对话。在修饰名词时，"a lot of"可以修饰可数名词和不可数名词，而"lots of"只能修饰可数名词。