Vinegar is, essentially, wine that has spoiled to the degree that all or most of the alcohol has oxidised to acetic acid. For the purposes of this page, however, we will follow the common usage and include alegar (made from oxidised beer), cidegar (made from oxidised cider) and other similar preparations.
Unsuprisingly vinegar is noticeably acidic and has a strong, bitter smell and taste.
Historically a waste product resulting from poor storage of fermented drinks, vinegar was quickly turned to a variety of uses. For a start, it can still be drunk if suitably diluted and was a common way of purifying drinking water if alcohol was not available or could not be used for some reason1. It can also be used as a preservative for pickling food or a seasoning in cooking and makes a passable topical disinfectant and cleaning agent2. Many cultures also use vinegar directly as a condiment, usually on high starch foods such as bread or potatoes (specifically chips).
Applied as a topical or poultice (typically on coarse brown paper or rags) vinegar could be used to treat bruising and sprains (presumably to some effect as the cure persisted for some time), used as a gargle or mouthwash it could be effective against throat infections and gum diseases.
Verjuice, made from the naturally sour juice of crab apples with the remaining sugar transformed more or less directly to acetic acid is very similar and was a significant seasoning and condiment in medieval cooking.