What is a skunked beer and how does it affect the taste and quality of the beverage?

A skunked beer is a beer that has been exposed to light, causing a chemical reaction that produces a foul, skunky odor and taste. This can happen when beer is stored in clear or green bottles and exposed to sunlight or artificial light for too long. The skunked flavor can overpower the original taste of the beer, making it unpleasant to drink and affecting its quality.