Brandy is a spirit produced by distilling wine. Brandy generally contains 35–60% alcohol by volume and is typically used as an after-dinner drink. Some brandies are aged in wooden casks, some are colored with caramel coloring to imitate the effect of aging and some brandies are produced using a combination of both aging and coloring.
Cognac is a specific type of brandy made from the grapes of the area surrounding the French town of the same name. Cognac must also follow strict guidelines to earn the title, similar to true champagnes.
Grappa is essentially an Italian brandy. It’s made in much the same fashion; distilling leftovers from the winemaking process.