Apple cider vinegar is a light golden color vinegar distilled from apples with a tart, fruity flavor. Use in salads and general purpose cooking. It can even be used to deglaze a pan for making a pan sauce.
Apple cider vinegar, diluted in water is said to be a very healthful ingredient. Many dieters swear by taking a 1-2 tablespoons of the vinegar with water, every morning. While there are many claims of health benefits there may or may not be scientific evidence that any of the health benefits are really a benefit. Here is a very good article about the topic by Science Driven Nutrition (Is apple cider vinegar a miracle food?).
You can purchase apple cider vinegar in most any grocery store. Bragg's is a good brand you can find at Whole Foods markets, Walmart, and possibly your local health food or grocery store.