The most common titles for wine experts are "sommelier" and "wine connoisseur." A sommelier is a waiter in high-end restaurants who has specialized training in wine tasting, judging and pairing with food, while a wine connoisseur is more of a hobbyist.
While a sommelier often requires training and certification, the term "connoisseur" typically refers to anyone who spends time learning and appreciating things that are considered higher class, like art, fine dining or wine. Any person can call themselves a connoisseur, but there is a distinction between a hobbyist and a professional. The original definition for "connoisseur" referred to someone being an expert in some sort of art or cuisine area, but has since widened to include amateurs.