Sweepings are the small bits of rubbish — dust, hair, crumbs, dead leaves, wood shavings, scraps of thread — that you push into a pile with a brush and then throw away. The word names the pile, not the action. It is always plural: 'the sweepings were thrown out', never 'a sweeping'. You meet it most in older writing and in places where sweeping up is part of the work: a bakery, a carpenter's workshop, a mill, a factory floor. Because sweepings are what is left over after everything valuable has been taken, the word is sometimes used about people or things in a cruel way, meaning the worthless leftovers nobody wanted — 'the sweepings of the streets'. That use is old-fashioned and insulting, so understand it in books but do not say it. Note that 'sweeping' on its own has other meanings entirely: as an adjective it means wide and total ('sweeping changes'), and it is also the -ing form of the verb sweep.