A Lot, Lots Of, A Lot Of
These three expressions are used in informal English. They can mean either a great quantity of or a large number of and can be rather confusing at times. Here are the general rules for their use.
A Lot Of / Lots Of
These two expressions both mean a great deal of or several. They are used before a count or non-count noun. These two expressions tend to be used in informal English.
We need a lot of people for this game.
She likes lots of jam on her toast.
Use a lot at the end of a sentence as an adverb. A lot is NOT followed by a noun. The meaning is the same as a great deal.
I enjoy swimming a lot.
Mary seems to travel a lot.