It means that you like most of society these days don't like chocolate that is sweet.
The U.S. government has rules that determine the composition and nomenclature of chocolate, which falls into one of five categories, and which is determined by its cacao content.
Unsweetened Chocolate, which is 100% cacao, is also called chocolate liquor. It is made from finely ground roasted cocoa nibs, and can be natural or Dutched (alkalized).
Bittersweet Chocolate ranges from 35% to 99% cacao content, so is by far the broadest category. It must contain at least 35% unsweetened chocolate and less than 12% milk solids. Virtually everything else is sugar. Within that range, you'll find all sorts of names: bittersweet, semi-sweet, dark, extra dark, extra bittersweet, etc. It used to be that bittersweet chocolate had an unsweetened chocolate content of 50% or more and semi-sweet contained 35% to 50%, but as chocolate tastes have swung towards less-sweet chocolate in recent years, many semi-sweets have crept into the 60%+ range.
Sweet Chocolate has a cacao content of 15% to 34%, and must also have less than 12% milk solids. Sweet Chocolate is more commonly called dark chocolate, although it has a lower cacao content than any in the bittersweet category. As a practical matter, this whole category apparently has no meaning. We have not been able, after many hours of hunting, to find a sub-35% chocolate that was not a milk chocolate.
Milk Chocolate contains at least 10% unsweetened chocolate, at least 12% milk solids, and at least 3.39% milk fat.
White Chocolate had no legal definition until recently because, as it has no chocolate liquor, technically it is not chocolate. The government was uncomfortable, though, knowing there was a substance on earth that it had not defined, so a fifth category was added to the chocolate standards of identity list, specifying that white chocolate must contain at least 20% cocoa butter, 14% milk solids, and 3.5% milk fat. It is also called white confectionary coating.
For baking with chocolate, knowing the percentage allows you to control the sweetness and chocolate intensity in your baked goods.