"A lot of" and "lots of" are quantifiers, or a sort of determiner, and are essentially an informal alternative to using "many" (for plural nouns) or "much" (for singular, mass nouns). ("Much" as a quantifier, in particular, sounds a bit stilted in everyday use, and so "a lot of" or "lots of" is more usual.) Note that although the former looks singular and the latter looks plural, you can use them both with either singular or plural nouns (so unlike "much"/"many" in that respect), with logical verb agreement, thus: "there's lots of tea left" or "a lot of people are going". Without "of" , these phrases can be used more as pronouns or adverbs rather than determiners: "there is lots left", "a lot are going" or "I am travelling a lot".

Hy Tiffany, There is no difference between a lot of and a lots of. they have the same mean. it might be used when you want refer to a large amount or a number of people or things. i hope i have help you. fell free to corect my inglesh. bye.

They're quantifiers, and they describe many or much of something. Some examples for each: 'a lot of' and 'lots of' can be used in the same way and are used to quantify something specific in a sentence: - There are a lot of books in the library. - There are lots of books in the library. - I have a lot of time tomorrow. - I have lots of time tomorrow. 'a lot' is used also as a quantifier but can be used more generally, and don't necessarily have to be tied to a specific object in the same sentence: - I like you a lot. - I have a lot.