Short for 'hundred-yen shop' — a store where many items are sold for 100 yen.
駅前に新しい１００均ができたらしい。
Apparently a new 100-yen shop opened in front of the station.
料理の道具は１００均でそろえた。
I got the kitchen utensils at the 100-yen shop.
旅行用の小物は１００均で買うことが多い。
I often buy small travel items at 100-yen shops.