The green stems are the part of the chives that are used as an herb. Chive stems are hollow and are usually used fresh. Chives are typically chopped and can be used as a garnish, although they do have a mild oniony flavor, especially fresh ones.
Chives can be featured in all sorts of recipes, from baked potatoes to soups, salads, sauces, and omelets. They're frequently mixed with cream cheese to make a savory spread. Chive butter, a compound butter made by blending chopped fresh chives into butter, is frequently served with grilled steaks or roasted poultry.
When you think of a baked potato, it's white (at least on the inside). You'll probably top it with butter and sour cream, also white, or at least pale yellow. Nor are any of the flavors of potato, butter or sour cream particularly pungent. Such is the appeal of chopped chives on a baked potato: It adds color and a contrasting flavor profile that pairs perfectly. Chives are good on just about anything. Their mild, oniony flavor pairs well with any savory dish, and the bright green color adds visual appeal as well.
One of the lovely things about chives, as compared to their cousins, scallions (also known as green onions or spring onions), is their delicate texture. Unlike scallions, with their wide tubes, chive stems are extremely narrow, which makes them particularly attractive as a garnish, whether chopped and sprinkled over a dish or draped whole across an entrée.
Chives are related to but are not the same as garlic chives. Garlic chives have wider, flatter stems which are not hollow, and they have a rather pronounced garlic flavor.
Chives are a wonderful herb to grow if you are feeling like you might like to start your own herb garden, even if it's just composed of a single herb. Chives grow well pretty much anywhere, provided they have enough sun and adequate water. And the beauty of them is that whenever you need some chive, all you have to do is go out and snip off however much you need. The stem will continue growing even after you've trimmed it. This means that a single good-sized chive plant will supply all the chives you are likely to need.
Chive plants develop bright purple blossoms that are edible and also have a mildly garlicky, oniony flavor. It's a good idea to remove them before they go to seed. Additionally, the stems on which the blossoms grow are tougher than the ordinary chive stems. So rather than just snipping off the blossoms and leaving the stems, snip off the whole stem, trim off the blossoms, and discard the stems.
The blossoms are great as a garnish, or you can sauté them or even roast them with chicken. Try making a chive butter with chopped-up purple blossoms instead. Or warm them up in some olive oil, then let the olive oil return to room temperature and use it to make chive blossom aioli.