Cats love the outdoors, but it's not safe to let your cat roam. You can fence your yard securely, using anti-climb topping, or you can buy (or make) a cat containment system that lets your cat experience the outdoors through a screen, but if you train your cat to walk on a leash, he can also enjoy short walks outdoors.
Although walking your cat won't be the brisk jog around the neighborhood that walking your dog can be, he'll still be able to sniff around, climb a short tree, get some exercise and generally break the monotony of his day. He'll also get to meet any neighbors who happen to see you and want to see the cat who walks on a leash! But be forewarned: Most cats prefer to walk where the neighbors won't notice them.