Taste is the ability to tell the difference between flavors in your mouth. It's your sense of taste that tells you if what you're eating is salty, sweet, or sour.
The verb taste means to perceive with your sense of taste ("I tasted kiwi for the first time") or to have a certain flavor ("the cake tastes of cinnamon and nutmeg"). The noun taste has a few different meanings. It's sensing flavors on your tongue, but it's also having a preference for something or a sense of discernment: "She has such good taste. Her clothes are always perfect." If you take a small sample of food, that's also a taste, as is a quick experience: "I only had a taste of what living in Paris would be like." Taste comes from the Old French taster, "to feel."