Often refers to leftover food, but can also be used for other remaining items or remnants.
I heated up and ate yesterday's leftovers.
会議の残り物の資料を片付ける。
I'll clean up the leftover materials from the meeting.
There are leftovers in the fridge.
I made curry out of leftovers.
I cleared away the leftovers from dinner.
I reheated yesterday's leftovers and ate them.