I dilly dally in couponing and technically this is a hot topic that people get angry about. In very simple terms, couponing is trying to get the lowest price possible. The lowest price for an item happens every couple of months. So in theory, you want to buy as much as during that moment so you can last during those months you're waiting for the next time. This is called a "stockpile".
There are couponers that love to show off their stockpiles. They'll have dozens of detergent in every brand and every size. They'll have food that'll last them for years even though it'll expire in a few months.
https://youtube.com/watch?v=0IqdtoIHtLc
https://youtube.com/watch?v=IJR6U6O6sIc
And the crazy thing is that they'll keep buying more and more and adding to their stockpile. Even though they can't eat it all and even though it's just sitting there. No family can use that much detergent in a few months let alone a few years.
The money you have to put into this is also insane. To coupon you need to get coupons from your local newspaper inserts. If you want multiple items, you need to get multiple coupons. This either means two things: you buy multiple coupon inserts off a website or you buy specific coupons off a website.
There are some couponers that actually do stuff with their stockpiles such as donate items and food. Some of them sell their items at flea markets and such. But most of them just collect it. It's just consoomerism but with extra steps and a self asspat of "But it was so cheap, so I had to buy all of them". This is hoarding, plain and simple.