Those are unique, handmade shopping bags made of 100% cotton. They are approximately 38 cm x 36 cm (the size may vary a bit since they are all uniqe). You can use them when going to the market, shopping goceries or as a library bags. I have one of those and I use it for carrying my lunch to work and when I'm going home from work, I stop at a store and buy food - the bag is strong enough for carrying all of that.
When not in use you can simply fold them and put them in your handbag. The size of folded bag is approximately 13 cm x 10 cm.