They look like basic balls of yarn, right?
Actually, they're dryer balls. I had a bit of this pretty Lion Brand Yarn in my stash, and it wasn't really enough to knit anything with it, so I decided to make some dryer balls. From what I've read, they're great at reducing static cling in the dryer and softening fabrics, without those dryer sheet things. I figure I'll give it a try, and see how well it works.
Here's how I made them.... I used 100% non-superwash wool, and simply wound it into a tight ball, roughly the size of a golf ball. Then I carefully placed the ball inside a small sock, and used cotton yarn to tie the sock closed, so that it was tight all around the ball. Then I put it in the washer with a load of laundry with the water set on hot wash, cold rinse. (Note: don't wash them in a load with bleach; bleach dissolves wool.) I put them through two cycles like that, then removed them from the socks. The wool had felted somewhat, so the balls didn't come unrolled. I even threw one across the room to be sure. ☺ Then I wrapped more wool yarn around the balls, until they were about the size of baseballs, and repeated the washing-inside-socks process. I also put them through a cycle in the dryer before removing them from the socks. They shrunk a little with the felting process, so they ended up about the size of tennis balls. (The blue ones ended up a little bigger than the more colorful ones.) I have a front-loading washer, which is great for laundry but not as efficient for felting, so if I had used a top-loader, they might have shrunk more. I haven't tried them out yet, because in the process of making them, I finished my laundry! But I'm sure there'll be more laundry in a day or two and I can try them in the dryer. From what I've read, they continue to felt a little each time you use them in the dryer, which will make them more dense, and even less likely to come apart. I can hardly wait to see whether the hype is true. I'll try to remember to post an update after I've used them.