Upside down planters are used to grow plants upside down. An upside planter looks like a bucket with all kind of sizes. They have a small hole in the bottom so that plants can grow downwards through that hole and they have with which they can be hang up.
Why are people using upside down planters? Well, a lot of people are using them because of the lack of space for planting a garden. Others are using them because otherwise pests will crawl into their plants and maintenance will be less when you hang your plants upside down.