Garlic leaves are in fact edible and many people tend to use them in salads as well as other dishes. There are lots of different culinary uses that garlic has, making it a very versatile herb. Leek and onion leaves are also edible for people and can be used in a variety of dishes, though you should probably avoid feeding them to pets such as dogs and cats as they can be poisonous to them.
Despite what many people think, there are actually a wide variety of tastes and textures associated with these leaves, so you will want to try many different kinds with the food you eat in order to enhance the overall taste of it.