Green Garlic is the spring (or sometimes fall) version of the cured bulbs you're used to seeing year-round at the grocery store. At this stage in the plant's life, the whole plant is edible and can be chopped up much like a scallion. It has a sweeter, milder flavor than when the bulbs are fully cured.
Try using green garlic in a stir-fry or chopped up with eggs. For a quick (and delicious) kitchen project, use green garlic instead of basil in your next batch of pesto.