“A lot of” or “lots of” can be used to substitute “much” or “many”.  It marks a large, unidentified amount.

She has many/a lot of ‘friends’, but only a few close friends.
I don’t have much/lots of money on me—I’d better go to the bank.

“A lot” or “lots” can also be an adverb, but without the ‘of’!

I love driving a lot.
I watch TV lots.  There are lots of great TV shows on cable!

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