Bouquet Garni is French for “garnished bouquet”. It is a classic herb mixture used for cooking meats, vegetables, and sauces. The traditional combination is parsley, thyme, and bay leaf although it is common to also include other herbs such as rosemary, basil, chervil, peppercorns, and tarragon. You can make a bouquet garni with fresh or dried herbs. If the herbs are fresh, the combination is secured with a bit of cooking twine, while cheesecloth is generally used to wrap the dried herbs, and the bundles are secured with twine. The pictures give you the full idea.
My experience is that using the bouquet garni has an additional benefit if your recipe would require filtering the floating herbs. Just pluck the bouquet garni out of the liquid being cooked and your soup or sauce is nice and clear of the herbs. A new discovery for me is that the top of leeks, which we normally cut and discard can be used instead of the little cheesecloth baggie if the herbs are fresh. Also displayed in the pictures.