Cats when playing are using skills similar to hunting behaviour. Cat play and toys incorporates predatory games. This allows your feline friend to grow and acquire cognitive skills, motor skills and socializing skills. The key is to understand the cats psychology. Cats are hunters, and stealthy ones at that. They love to be able to sneak up on something. Toys ranging from strings, to small furry toys resembling prey to plastic bags and cardboard boxes, can promote these traits - just about anything can become a cat toy.
Cat toys can actually provide a useful function as well as being fun. When caring for your cat, it can be nice to keep distracted and occupied to minimise destructive behaviour. They will chase streamers around, getting tangled in balls of yarn, and even play tug-of-war on occasion.
Of course, having the right cat toys helps, make sure the materials are feline safe and your pet is supervised at play. If it has something shiny and the end of it bobs up and down in an interesting and animated manner, so much the better. Kitty will stalk, waiting for the right moment to pounce. When it does, you can yank up out of reach just in the nick of time. It helps if you let the cat catch the cat toys every once in a while, they can be snobs and stop playing with you.