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. Examples: We need a lot of people for this game. She likes lots of jam on her toast. A Lot 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. Examples: I enjoy swimming a lot. Mary seems to travel a lot. http://esl.about.com/od/grammarintermediate/a/cm_lot.htm

"lots of" sounds a bit more informal than "a lot of".