A barista is a café employee who specializes in coffee drinks, especially espresso. The person who makes your half-caf vanilla caramel latte is a barista.
In Italy, a barista is a "bartender serving coffee drinks, alcoholic drinks, and snacks." The word was adopted by English-speakers around 1992, at the start of the craze for espresso bars and cafés outside of Italy. If a restaurant only serves drip coffee, the person making it isn't called a barista. An espresso machine, on the other hand, requires a barista. If your specialty coffee drink is always delicious and served with a smile, be sure to tip your barista!