Often the opposite of complex. A naturally occurring chemical that helps to preserve red wine. Generally speaking 'fine' quality tannins are less astringent and easier to taste than 'hard' or 'coarse' tannins, which tend to sting the inside of the mouth. Can also mean a wine that is 'forward' in nature. A term used to describe the texture and overall impression of a wine's body.
Words commonly used are thick, thin, heavy, light or dense.