Couverture [koo-vehr-TYOOR] n. Glossy chocolate designed for coating with very high ratio of cocoa butter.
Couverture is a professional confectionary term for chocolate that has at least 32% cocoa butter, and usually as much as 35% to 39%. This higher cocoa butter content allows the chocolate to form a thinner, more delicate coating on candies and pastries, and it also has a much higher liquidity. In other words, when you melt it it's going to be thinner and more liquid and thus more easy to pour.
Couverture is usually only found in specialty baker's shops or catalogues, but if you're doing a lot of dipped or coated candies this holiday season, it may be worth searching out. Callebaut has a particularly helpful website which even includes a guide to determining the right chocolate viscosity for a particular recipe.