Looks like a green cherry tomato in a paper husk. Also called a Mexican green tomato, Mexican husk tomato, Tomate Verde. You peel the parchment cover off and wash the little tomato well. Tomatillos are most often cooked in salsa. They have a lemony flavor. If you eat them raw, they are more sharply acidic. They can be stored in the refrigerator for a very long time.
You can try them chopped in salad, in gazpacho, or you can cook them into a sauce for tacos and enchiladas. Poach the peeled and washed tomatillos very briefly, then combine with chili peppers, onion, garlic, cilantro and salt.